How to Make It
Preheat oven to 350°F. Prepare the Topping: Stir together flour, chopped pecans, granulated sugar, brown sugar, and salt in a medium bowl. Stir in butter until well combined. Chill until ready to use.
Prepare the Cake: Beat sugar and butter in a medium bowl with an electric mixer on medium speed until mixture looks sandy, 2 to 3 minutes. Add egg, and beat until well combined. Beat in vanilla.
Whisk together flour, baking powder, and salt in a medium bowl. Alternately add flour mixture and milk to butter mixture in 5 additions, beginning and ending with flour mixture. Beat until combined after each addition. Gently fold in 1⁄2 cup each of the chopped peach and raspberries.
Transfer batter into a greased (with butter) and floured 9-inch springform pan. Arrange remaining 1⁄2 cup each of the chopped peach and raspberries in an even layer over top of batter.
Sprinkle chilled Topping evenly over the fruit. Bake in preheated oven until browned and a wooden pick inserted in center comes out clean, 40 to 45 minutes.
Cool in pan on a wire rack 15 minutes. Run a knife around edge of pan to loosen Cake from sides. Remove sides of pan. Cool on wire rack about 45 minutes. Serve warm or at room temperature.