Prepare streusel topping. Beat butter with an electric mixer until creamy; gradually add sugar and brown sugar, beating well. Add flour, cinnamon, and nutmeg; beat until blended.
Prepare batter. Beat butter at medium speed with an electric mixer until creamy; gradually add sugar, beating well. Add eggs, 1 at a time, beating until blended after each addition. Combine flour, baking powder, and salt; add to butter mixture alternately with milk, beginning and ending with flour mixture. Beat at low speed until blended after each addition. Stir in vanilla.
Pour batter into a greased and floured 9-inch springform pan; top with sliced peaches and blackberries.
Pinch off 1-inch pieces of streusel topping, and drop over fruit.
Bake at 350° for 1 hour and 10 min. to 1 hour and 20 min. or until center of cake is set. Cool completely on wire rack.
Recipe by Kuhn Orchards at https://kuhnorchards.com/blackberry-peach-coffee-cake/