Preheat oven to 350 degrees F and grease an 8.5in x 4.5in loaf pan with non-stick spray or butter.

Mash 1 cup of overripe bananas and combine with 1 Tbsp of freshly squeezed lemon juice. This prevents the bananas from browning and brightens up their flavor. Set aside.

Add 1/3 cup unsalted butter and 1/2 cup granulated sugar into a large bowl. Beat on a medium high speed for 2-3 minutes with either a hand mixer or a stand mixer with a whisk attachment. Beat until the mixture becomes lighter in color.

Mix in 1 large whole egg + 1 egg white on a medium speed, and continue to mix for an additional minute, until the mixture should be fluffy and light. Scrape the sides and bottom of the bowl as needed with a rubber spatula.

Add in 1 1/2 tsp baking powder, 1/2 tsp baking soda, salt, and 1 cup of all-purpose flour. Mix on a low speed until just combined.

Pour in 1/3 cup of milk, and mix on a low speed until it's incorporated.

Add in the remaining 3/4 cup of flour, and mix on low just until you can no longer see streaks of flour.

Mix in the mashed banana/lemon juice mixture on a low speed until it is fully incorporated into the batter. Fold in 2/3 cup of rainbow sprinkles

Pour the batter into the prepared pan.

Bake on the upper baking rack for 55-65 minutes, rotating the pan half way through to make sure it bakes evenly. If you notice the top of the loaf is browning quickly when you rotate it, cover the loaf pan with a foil tent to prevent it from over browning.

Remove the loaf from the oven, and let it cool in the pan for 10 minutes. Transfer to a wire rack to finish cooling.

Place 1 1/2 cups powdered sugar, 1 Tablespoon butter, 2 Tablespoons milk, and 1 tsp of vanilla extract in a medium-sized bowl. Whisk together until smooth and no clumps remain.

This glaze hardens as it sits, so cover it with plastic wrap if you don't plan to use it immediately.

Pour on the cooled loaf of funfetti banana bread, and top with an additional 1/2 cup of sprinkles.