Preheat your oven to 350°F (175°C). Grease or line your baking pan with parchment.

In a small bowl, mix brown sugar and flour. Add softened butter and mix until crumbly. I like using my fingers to get that perfect crumb texture.

In a large bowl, whisk together flour, baking powder, and cinnamon.

In another bowl, beat the softened butter, brown sugar, sour cream, egg, milk, and vanilla until combined. Slowly add the dry ingredients to the wet. Don’t overmix—just until everything’s combined.

Gently stir in the peach slices. Pour the batter into the prepared pan and spread it evenly.

Sprinkle the crumb topping over the batter. Try to cover as much as you can—it’ll bake into a golden, crispy layer.

Bake for 38–42 minutes or until a toothpick in the center comes out clean and the top is golden brown.

While the cake cools a bit, whisk together powdered sugar, milk, and cinnamon. Drizzle over the warm cake. Let it set before slicing (if you can wait!).