Preheat the oven to 350°F (175°C) and grease a 9-inch cake pan.
In a bowl, whisk together flour, baking powder, baking soda, and salt.
Cream butter and sugar until fluffy.
Add eggs one at a time, mixing well after each.
Stir in sour cream and vanilla extract.
Gradually add dry ingredients to the wet mixture, mixing until combined.
Gently fold in peaches and blueberries.
Pour batter into the cake pan and smooth the top.
For the topping, combine flour, brown sugar, melted butter, and cinnamon. Sprinkle over the batter.
Bake for 50 minutes or until a toothpick comes out clean. Cool before serving.