In a large mixing bowl, whisk together the dry ingredients ( flour, baking powder, soda and salt ). Set aside.
Preheat oven to 350 degrees F.
If using sour milk, place 1 tablespoon of white vinegar into a measuring cup and fill with milk to make 1 cup of liquid total. Stir few time and let sit.
In a large mixing bowl of a stand mixer, mix egg yolks with granulated sugar, until pale and creamy on medium speed.
Add vanilla and egg whites and mix well.
Lower the speed to low and add the dry ingredients in three parts alternating with buttermilk.
Mix well.
Pour into prepared skillet. Bake the cake for 15 minutes. Do nut turn off the oven. Arrange the fruit on the partially baked cake. Return to the oven and bake until golden and the sides are browning, about 15 more minutes. Cool completely in the skillet.