Preheat oven to 350°F. Line four, six-inch pans with parchment rounds, and grease with non-stick cooking spray.

Mix together all dry ingredients (flour, baking powder, sugar, and salt) in a stand mixer with a paddle until fully combined.

Mix chunks of room-temperature butter slowly into the dry mix, on a low speed. Continue to mix until no large chunks of butter remain, and the mixture becomes crumbly.

Pour in egg whites, and mix on low until just incorporated. Mix in the buttermilk in two installments, on a low speed.

Add in lime juice, lime zest, and oil, and mix at a low speed until fully incorporated.

Divide batter evenly between the prepared cake pans (about 300 grams per pan).

Bake for 32-35 minutes, or until a toothpick comes out clean.

Allow the pans to cool for 10 minutes, then run an offset spatula around perimeter of the pan to separate the cake from the pan.

Place cake layers into the freezer for 45 minutes, to accelerate the cooling process. Once the layers are fully cooled, carefully flip the pans and remove the layers.

Use a serrated knife to level the tops of the layers.

Place water and sugar in a pot.

Heat over high heat, stirring occasionally until the mixture just begins to boil.

Remove from heat, and allow the mixture to cool for 10 minutes.

Add in the tequila, lime zest, and lime juice, and set aside.

While the cake layers bake and cool, make the tequila frosting.

Beat the butter on a medium speed for 30 seconds with a paddle attachment, until smooth. Slowly add in the powdered sugar, 1 cup at a time. Alternate with small splashes of the lime juice and tequila.

Once fully mixed, add in the lime zest and salt, and beat on low until the ingredients are fully incorporated, and the desired consistency is reached. 

If the frosting is too thick, add in additional lime juice (1 teaspoon at a time). If the frosting is too thin, add in more powdered sugar (quarter of a cup at a time).

Divide the frosting into five bowls, adding an extra cup of frosting to the bowl you plan to color green.

Color the frosting bright green, orange, pink, yellow, and blue with gel food coloring

Place each color of frosting into its own piping bag, fitted with a wilton 104 frosting tip.

Once the simple syrup has cooled, dab it on top of each leveled cake layer, using a sterile brush. Be sure to fully cover the surface of each cake layer.

Stack and frost cake layers on a greaseproof cake board, using a dab of frosting to help stick the first cake layer to the board.

If desired, use a three-inch circle cutter to remove the center from the two middle cake layer to make a sprinkle filled cake.

Pipe about 1/2 cup of green frosting on top of each cake layer, and spread with an offset spatula.

While assembling the cake, fill the hole in the middle cake layer with a festive sprinkle blend to create a piñata-inspired cake.

Apply a thin coat of green frosting around the the cake, to fully cover the cake layers. Smooth using a bench scraper, then chill the cake in the fridge (10 minutes) or freezer (5 minutes) until the frosting is firm to the touch.

Pipe vertical ruffles of buttercream up the sides of the cake, following the same color pattern.

Use leftover buttercream to pipe small flowers to decorate the top of the cake.