In a medium bowl, whisk all-purpose flour, cornstarch, salt, baking powder, and baking soda
Using an electric mixer with a large bowl beat the butter until creamy
Add the sugar and beat until well blended
Add the eggs and vanilla and mix in
In a small bowl, mix the milk and sour cream
Mix in the sour cream mixture into the batter - only until mixed in
Pour in the dry ingredients and mix until blended
Place a baking sheet under your cake pan to catch any loose batter
Pour the thick batter into the cake pan
Bake for about 1 hour
Remove the cake and let it cool completely
Slice the cake in half and slice the top portion off of the cake
Let the 2 halves of the cake cool completely