1. Preheat Oven: Preheat your oven to 350°F (175°C). Grease and line a square baking pan.
2. Prepare the Cake Batter:

In a bowl, mix flour, baking powder, baking soda, and salt.

In another bowl, beat butter and sugar until fluffy. Add eggs one at a time, then mix in vanilla.

Gradually mix in dry ingredients and buttermilk, alternating, until combined.

3. Assemble the Cake:

Pour the batter into the prepared pan.

Evenly spread the diced peaches over the batter.

4. Prepare the Crumble Topping:

Mix sugar, flour, cinnamon, and cold butter with your fingers or a fork until crumbly.

Sprinkle the crumble evenly over the peaches.

5. Bake:

Bake for 40–50 minutes, or until a toothpick inserted in the center comes out clean.

6. Cool and Serve:

Let the cake cool in the pan for 15 minutes, then transfer to a wire rack. Slice and serve.

Enjoy your peach crumble cake!