Preheat your oven to 350°F (175°C) and grease a 9-inch round cake pan.

In a large mixing bowl, whisk together all-purpose flour, baking powder, baking soda, salt, brown sugar, and granulated sugar.

In another bowl, beat together unsalted butter and brown sugar until light and fluffy. Blend in the granulated sugar until smooth.

Add eggs one at a time, mixing well after each addition.

Gradually mix in milk until just combined.

Fold in the diced fresh peaches gently into the batter.

Pour the batter into the prepared pan and smooth the top.

Mix together brown sugar and ground cinnamon for the topping and sprinkle over the batter.

Bake for 30-35 minutes until a toothpick comes out clean.

Let the cake cool in the pan for about 10 minutes before transferring to a wire rack.