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

In a bowl, toss sliced peaches with sugar if desired.

Whisk together flour, baking powder, and cinnamon in another bowl.

Cream together softened butter and sugar until fluffy in a separate bowl. Add eggs one at a time, mixing well after each addition.

Stir in milk and vanilla extract until just combined; do not over-mix.

Gradually incorporate the dry mixture into the wet ingredients until blended. Gently fold in peach slices.

Pour the batter into the prepared pan and bake for 40-45 minutes or until golden brown and a toothpick comes out clean.

Allow to cool before slicing.