Preheat oven to 350 degrees F. Line cupcake tin with paper liners. In a medium bowl, whisk together cake flour, baking powder, baking soda and salt. Set aside.
In separate bowl, use electric mixer to beat eggs. Add sugar and continue mixing on medium speed.Add vanilla and squash, continue mixing. Reduce mixer speed to medium-low and slowly add about half the flour mixture Add half the buttermilk, then the rest of the flour mixture and the milk. Batter should be thin.
Pour batter into lined pan, fill to about 1/2 full.
Bake for 12-14 minutes. Let cool before removing from pan.