- Topping: In a small bowl, blend together all ingredients until the mixture resembles coarse meal. Chill the topping while making the batter.
- Batter: In a large bowl with an electric mixer, cream the butter and sugar together, beat in the vanilla.
- In a small bowl, stir together baking powder, flour and salt.
- Alternately beat the flour mixture and eggs into the butter mixture. Add an egg each time beating well after each addition.
- Fold in the blueberries and nectarines.
- Preheat oven to 350 degrees. Spread the batter in a well-greased 9x13 inch baking pan. Sprinkle the topping evenly over it.
- Bake at 350 degrees for 45-50 min or until knife inserted comes out clean and topping is crisp and golden.