Apple Cake in an Iron Skillet

Name: Apple Cake in an Iron Skillet
Ingredients: 1 stick unsalted butter; 3/4 c. granulated sugar; 4 whole granny smith apples, cored, halved and each half cut into six equal pieces; 1 stick butter, softened; 2/3 c. granulated sugar; 1 1/2 tsp. vanilla extract; 2 large eggs; 1/2 c. sour cream, room temperature; 1 1/2 c. all-purpose flour; 1 1/2 tsp. baking powder; 1 tsp. salt; 1/2 tsp. ground cinnamon; 1 granny smith apple, peeled, cored and chopped finely; Vanilla ice cream, for serving