This lemon Swiss meringue buttercream is made with fluffy, whipped meringue and has the perfect balance of bright citrus flavor & sweetness!

It pipes like a dream, and I love using it to frost cakes, cupcakes, pies, and cookies.

How to Make Lemon Swiss Meringue Buttercream

Let’s walk through everything you need to know to make the smoothest, fluffiest lemon Swiss meringue buttercream!

I’ve also shared a video below if you’re more of a visual learner.

Step #1: Separate the Egg Whites

What gives this frosting its incredible texture is the meringue that it’s made with. That’s why the eggs in this recipe are so important. Or more specifically the egg whites!

I recommend separating the eggs when they’re cold. It makes it way easier, and they’ll be heated before being whipped so there’s no need to bring them to room temperature ahead of time.

Be careful as you do this because they won’t whip up properly if any yolk gets into the mixture.

If you’re not sure what to do with the egg yolks you’ll be left with after making this frosting, here’s a great post with loads of ideas for using up leftover egg yolks.

Normally I’m a huge fan of using egg whites out of a carton, but that’s when I’m adding them into a batter.

I don’t recommend using egg whites from a carton to make Swiss meringue frosting. However, you can use them to make my hybrid buttercream frosting.

Step #2: Heat Up the Egg Whites & Dissolve the Granulated Sugar

By heating up and whisking our egg whites and granulated sugar over a double boiler to 160 F / 71 C, we accomplish two things at once.

The first is that we kill any potentially harmful bacteria. Salmonella is killed at this temperature.

The second is that it dissolves the granulated sugar, which gives the frosting a silky-smooth texture.

The easiest way to ensure the mixture gets hot enough is to use a digital thermometer. This helps you know exactly when the egg whites are warm enough and prevents you from overheating them.

If you don’t have a digital thermometer on hand, you can test the mixture by rubbing a tiny bit between your fingertips. The sugar should be fully dissolved, and it should feel super smooth and hot to the touch.

If you do feel sugar granules, I suggest heating the egg white/sugar mixture a bit longer, then testing it again to make sure it’s smooth.

It’s very important that the sugar is fully dissolved before you make the meringue, or else your frosting can end up with a grainy texture.

Step #3: Whip the Swiss Meringue to Stiff Peaks

Once the sugar is fully dissolved and the mixture is smooth, it’s time to whip the meringue until it has stiff peaks. This takes quite a bit of time!

It usually takes me about 10 minutes with a stand mixer and whisk attachment on a medium-high speed (8 on a Kitchen Aid).

While the meringue whips, I like to add something cold around the base of my bowl.

I find the meringue stays quite warm while it whips up and placing a bag of frozen veggies around the base of the bowl helps cool it back to room temperature. This can prevent your buttercream from becoming soupy in the next step.

You can also make this Swiss meringue buttercream with a hand mixer, but it takes forever!! Making it with a stand mixer is much easier and quicker.

Once the meringue has stiff peaks, it should look like the photo below. The meringue should be able to stand up on its own when flipped upside down, and it should look shiny.

It can be hard to tell when the meringue reaches this stage just by looking at your mixing bowl, so feel free to take breaks and test it by removing the whisk attachment and flipping it upside down.

Step #4: Add in All the Good Stuff

After all that mixing, you’d think your bowl would have fully cooled off, right? But you might be wrong! At this point in time, I recommend feeling the bottom of the bowl with your hand.

If it feels like it’s pretty much at room temperature, then add in the butter. If it still feels warm, either wait another 15 minutes to add the butter or pop the bowl into the fridge for 5 minutes to help it cool down.

Usually, by making sure the meringue and bowl have cooled to room temperature, you can prevent your Swiss meringue buttercream from becoming too thin or soupy.

When you do start to add in the unsalted butter, add it one stick at a time. This gives your meringue time to incorporate the butter and helps it come together more easily.

As you add the butter, it’s super important that the butter is at room temperature. This does NOT mean soft to the touch or greasy.

It should be soft enough for you to press your finger into, but firm enough that you have to apply a bit of pressure to do so.

The time it takes for a stick of butter to come to room temperature can vary based on the type of butter you use and the temperature and humidity of your kitchen. In my kitchen, it usually takes 1-2 hours (1 hour in the summer, 2 hours in the winter).

Once the butter is mixed in, the frosting should look fluffy and light like it does in the picture below.

If your frosting looks curdled or soupy at this point, please refer to the troubleshooting section below.

Next, add the lemon zest, fresh lemon juice, vanilla extract, lemon extract, and fine salt and mix until combined. If you want to add gel food coloring, I recommend adding it at this point in the process.

Step #5: The Attachment Switcheroo

When all the ingredients are mixed in, it’s time to swap out your whisk attachment.

While we want our buttercream to be fluffy and light in texture, we also want it to be smooth.

Whether you plan to spread your frosting onto a cake or pipe with it, the frosting needs to be smooth and free of air bubbles.

I find that mixing the finished buttercream on a low speed with a paddle attachment for a few minutes makes a world of a difference. It makes it so much easier to smooth onto cakes!!

Lemon Swiss Meringue Buttercream Troubleshooting

Two of the most common issues people run into when making this type of buttercream are curdled or soupy frosting.

While it might seem terrifying to watch your frosting seem to fall apart, fear not. Both problems are actually pretty easy to fix!!

How to Fix Curdled / Broken Lemon Swiss Meringue Buttercream

A lot of different things can cause SMBC to break or curdle.

Maybe your butter was too cold, or your kitchen was too chilly. Maybe you were thawing a batch of buttercream made in advance, and it hadn’t fully come to room temperature before you started mixing it.

Whatever the reason, your frosting looks chunky, dense, watery, and greasy.

But don’t worry, your frosting isn’t ruined! There’s an easy workaround that will bring the frosting back together.

Simply place the bowl over a hot water bath / double boiler until the frosting around the edge of the bowl has melted. Then give it a good mix on a medium speed for about 5 minutes.

The melted, warm buttercream around the edge of the bowl will mix with the frosting that’s too cold.

This will bring the overall temperature of the buttercream up to the right temperature and allow it to become smooth again.

How to Fix Soupy Lemon Swiss Meringue Buttercream

On the other hand, if your frosting is too warm it might become a soupy, runny mess.

This can happen if the meringue was too warm when you added the butter, if the butter is too warm, or if your kitchen is too toasty!!

If the buttercream isn’t sturdy enough to keep its shape, you need to cool it down. To do this, just pop the mixing bowl and whisk right into the fridge.

Chill the bowl in the fridge for 10-20 minutes or the freezer for 5-10 minutes.

At this point, the center might still be a bit soupy, but the buttercream along the sides of the bowl should be firmer. Then mix the buttercream for a few minutes to see if it comes together.

If after 3-4 minutes of mixing it still looks too soft, chill the bowl for another 10 minutes before mixing it again. That usually does the trick!

Can I Color This Lemon Swiss Meringue Buttercream Frosting?

Short answer – yes! You can color this buttercream.

However, this type of frosting is a bit more difficult to color than American buttercream. To make it bright and colorful, gel food coloring is a must.

My favorite gel food coloring is Americolor, and it’s the only food coloring I use. 

Even with gel food coloring, I have to use quite a bit to get my colors really vibrant.

If you want to make deep or really intense colors, I highly recommend making your frosting in advance. The color of the frosting will deepen over time!

You can also use the microwave method to deepen the color.

To do this, scoop 1/2 cup of the finished buttercream into a microwavable bowl. Add additional gel food coloring and mix until the frosting reaches the desired color.

Then microwave the frosting for about 15 seconds. The frosting should be runny but deeper in color. Mix this back into the full bowl of frosting and you should achieve a deeper color.

If you end up using this method, let your frosting sit for about 30 minutes before you use it to allow it to thicken back up.

How Much Buttercream Does this Recipe Make?

One batch of this recipe makes about 7 cups of frosting.

This should be enough to fill and frost a seven- or eight-inch layer cake, or frost 2-3 dozen cupcakes (depending on the size of your swirls).

This recipe can be halved, but I don’t recommend doubling it unless you have a commercial size KitchenAid (8 qt). Otherwise, it can be really difficult to whip up the meringue to stiff peaks.

Tips For Making the Best Lemon Swiss Meringue Buttercream

• Wipe down your tools with lemon juice or vinegar to make sure they’re grease-free. Traces of grease in the mixing bowl can prevent the meringue from forming stiff peaks!
• Separate the eggs when they’re cold! It makes it way easier, and they’ll be heated before being whipped so there’s no need to bring them to room temperature.
• Heat the egg white / sugar mixture to 160 F / 71 C and check to make sure all the sugar is dissolved before removing it from the double boiler.
• Whip the meringue until its peaks are stiff enough to defy gravity.
• Make sure the butter is actually at room temp and add it in gradually (1 stick at a time).
• When in doubt (if the frosting breaks / curdles), just keep mixing!! It should come back together with the help of your stand mixer and a little more time. If it doesn’t, please check out the troubleshooting section above.
• Mix the finished buttercream on the lowest speed with a paddle attachment for a few minutes to make it super smooth. This pushes out any excess air and will make it easier to smooth onto a cake.

Making This Lemon Swiss Meringue Frosting in Advance and Storage Tips

Make this frosting ahead of time or save any leftover frosting! It can be stored in an airtight container at room temperature for up to 2 days, in the fridge for up to 2 weeks, or in the freezer for up to 3 months.

Be sure to give it a good stir once it thaws to room temp to get the consistency nice and smooth again.

A frosted cake can last in the fridge for up to a week or in the freezer for up to a month. The buttercream locks in all the moisture, keeping the cake fresh and delicious!

Let Me Know What You Think!

If you try this lemon Swiss meringue buttercream recipe, I’d love to hear what you think of it! Please leave a rating and comment below.

Tag me @chelsweets and use #chelsweets so that I can see your amazing creations on social media!

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