Preheat your oven to 350°F (175°C). Peel and slice the peaches, then set aside.

In a large mixing bowl, cream together the softened butter and granulated sugar until light and fluffy.

Add the eggs one at a time, mixing well after each addition, then stir in the vanilla extract.

In a separate bowl, whisk together the flour, baking powder, salt, and ground cinnamon (if using). Gradually add this dry mixture to the butter mixture, alternating with the milk, mixing until just combined.

Gently fold in the sliced peaches into the batter.

Pour the batter into a prepared 9-inch round cake pan and spread evenly. Bake for 40-45 minutes, or until a toothpick inserted into the center comes out clean.

Let the cake cool in the pan for about 10 minutes, then transfer to a wire rack to cool completely. Dust with powdered sugar before serving.