Preheat oven to 350 degrees.
Line cupcake pan with paper liners.
Sift flour, baking powder, salt, and baking soda together in a bowl.
Beat butter on high for 30 seconds.
Add sugar and vanilla extract to the butter until well combined.
Add egg whites, one at a time, mixing after each.
Add eggs, one at a time, mixing after each.
Add 1/3 cup flour mixture to the wet mixture followed by adding 1/3 cup of the buttermilk; add 1/3 cup flour mixture again then add 1/3 cup buttermilk mix on low-speed, add 1/3 cup of flour and add the rest of 1/3 cup of buttermilk mix in low-speed until thoroughly blended.
Divide the batter into two bowls. Add red gel food colouring to one bowl and stir well. The second bowl remains white.
Begin by spooning in some of the red batter then add the white on top of the red. Continue with the a spoon of the red again then the white all around the individual lined cupcake tins.
The batter will spread out in the cupcake tin but continue to layer the batter with the red then the white.
The batter should reach 2/3rd of the top of the lined cupcake holders.
Bake at 350 degrees for 20-25 minutes or until an inserted toothpick comes out clean.
Cool for 10 minutes.
Remove to a wire rack until fully cooled