Step 1

Preheat oven to 350 degrees. Sift all-purpose flour and cake flour into a mixing bowl. Add baking powder, baking soda and salt and whisk 20 seconds, set aside.

Step 2

In a food processor, pulse together 3/4 cup + 2 Tbsp granulated sugar with lime zest until finely ground, about 1 minute.

Step 3

In the bowl of an electric stand mixer fitted with the paddle attachment, whip together butter with lime sugar mixture until pale and fluffy. Scrape down bowl.

Step 4

Mix in egg, then mix in egg whites one at a time, adding in vanilla with second egg white. Scrape down bowl.

Step 5

In the liquid measuring cup used to measure buttermilk, whisk together buttermilk with lime juice. Working in three separate batches, beginning and ending with flour mixture, add 1/3 of the flour mixture alternating with 1/2 of the buttermilk mixture and mixing just until combined after each addition. Scrapw down bowl and fold batter gently.

Step 6

Divide batter among 12 paper lined muffin cups. Bake in preheated oven until toothpick inserted into center of cupcake comes out clean, about 18 - 20 minutes.

Step 7

Remove from oven and allow to cool several minutes in muffin tin, then transfer to a wire rack to cool slightly while preparing simple syrup.

Step 8

For the simple syrup:

Step 9

In a small bowl, whisk together 1 Tbsp lime juice with 1 Tbsp granulated sugar until sugar has dissolved. Brush mixture over warm cupcakes (use all of it, I did about 2 light coats over each cupcake). Allow cupcakes to cool completely.

Step 10

For the frosting:

Step 11

In the bowl of an electric stand mixer fitted with the paddle attachment, whip butter until pale and fluffy. Mix in 1/4 cup powdered sugar then mix in maraschino cherry juice and optional red food coloring.

Step 12

With mixer set on low speed, slowly add remaining 2 1/4 cups powdered sugar (add an additional 1/4 as needed to reach desired consistency), then increase mixer to medium and whip until light and fluffy.

Step 13

Pipe or spread over cooled cupcakes, top with each with a maraschino cherry and a lime slice and sprinkle edges with sprinkles if desired.