Preheat the oven to 350°F. Line a 12-cup muffin pan with cupcake liners.

In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.

In a large bowl, beat the softened butter and sugar with an electric mixer until light and fluffy.

Add the whole egg, then the egg whites one at a time, mixing well after each addition. Mix in the vanilla extract.

Add the buttermilk and mix until combined.

Gradually add the dry ingredients to the wet ingredients and mix just until combined. Do not overmix.

Divide the batter evenly among the cupcake liners, filling each about ¾ full.

Bake for 20–25 minutes, or until a toothpick inserted into the center comes out clean.

Let the cupcakes cool in the pan for 10 minutes, then transfer them to a wire rack to cool completely before frosting.

Beat the softened butter until smooth and creamy.

Gradually add the powdered sugar, alternating with the Orange Crush soda, and beat until smooth.

Add orange gel food coloring until the desired color is reached.

If the frosting is too thick, add a small amount of additional soda. If it is too thin, add more powdered sugar.

Transfer the frosting to a piping bag fitted with a large decorating tip and frost the completely cooled cupcakes.