1/2 cup butter at room temperature
3/4 cup sugar
1 teaspoon vanilla
2 cups flour
1 teaspoon baking powder
1 teaspoon baking soda
1/4 teaspoon salt
1 cup sour cream
6 tablespoons butter at room temperature
1 cup brown sugar
2 teaspoons cinnamon
1 cup chopped nuts (optional)
Preheat oven to 350º. Grease angel food pan with butter. Cut piece of wax paper or parchment to line bottom of pan. Place parchment in bottom of greased pan, and grease the top of the paper.
Cream butter and sugar. Add vanilla, then mix in eggs, one at a time.
Sift together flour, baking powder, baking soda, and salt.
Add dry ingredients and sour cream to the creamed mixture, alternating, starting and ending with the dry ingredients.
Mix first 3 streusel ingredients; add nuts if desired.
Put half the batter in prepared pan. Sprinkle with half the streusel. Add the rest of the batter, then smooth the top. Sprinkle with the remaining streusel topping.
Bake for 45-50 minutes. Cool 10 minutes. Remove from pan to serving plate. Sprinkle with powdered sugar to serve.