Preheat oven: Preheat your oven to 350°F (175°C). Grease and lightly flour your baking pan or line it with parchment paper.
Prepare the batter:
In a medium bowl, whisk together flour, baking powder, and salt.
In a large bowl, cream the butter and sugar until light and fluffy. Add eggs one at a time, beating well after each addition. Mix in vanilla extract.
Gradually add the dry ingredients to the wet mixture, alternating with milk, starting and ending with the dry ingredients. Mix until just combined.
Assemble the cake: Pour the batter into the prepared pan, spreading it evenly. Arrange the peach slices on top of the batter in a decorative pattern. Sprinkle with sugar and cinnamon (if using) for a sweet and spiced topping.
Bake: Place the cake in the oven and bake for 40–45 minutes, or until a toothpick inserted into the center comes out clean.
Cool and serve: Allow the cake to cool in the pan for 10 minutes before transferring it to a wire rack to cool completely. Serve warm or at room temperature.