01 - Preheat oven to 350°F. Grease and flour a 9-inch round cake pan or springform pan.
02 - Whisk together flour, baking powder, baking soda, and salt in a medium bowl.
03 - Beat melted butter and sugar in a large bowl until smooth. Add eggs one at a time, mixing well after each. Stir in sour cream and vanilla extract.
04 - Fold dry ingredients into wet ingredients until just combined. Do not overmix.
05 - Gently fold in two-thirds of the peach slices.
06 - Pour batter into prepared pan and smooth top. Arrange remaining peach slices on top in a circular pattern.
07 - Mix sugar and cinnamon in a small bowl. Sprinkle evenly over peaches.
08 - Bake for 38-42 minutes until toothpick inserted into center comes out clean and top is golden brown.
09 - Cool in pan for 10 minutes. Run knife around edge and release cake onto wire rack to cool completely.
10 - Serve slightly warm or at room temperature, plain or with whipped cream.