Start by preheating your oven to 350° then place cupcake liners in two 12 cup muffin pans.
In your mixer bowl, add softened butter and beat for about 2 minutes on high speed. Slowly add in sugar and beat until fluffy.
In a separate bowl, whisk together dry ingredients: flour, cornstarch, baking powder, baking soda & salt.
Next, add eggs one at a time to the butter mixture, mixing after each addition then add vanilla extract.
Reduce mixer speed, then add the four mixture slowly. Beating well to combine. Alternate adding half of the buttermilk, then more flour, then the rest of the buttermilk until a smoothe batter forms.
Pour batter into your lined muffin pans, filling ¾ full. Bake for 20-25 mintes until a toothpick comes out clean. Let cool completely before frosting.