1-Wash the peaches thoroughly, slice them in: Wash the peaches thoroughly, slice them in half, remove the pits, and cut them into wedges.
2-In a small saucepan, melt 1/4 cup: In a small saucepan, melt 1/4 cup of unsalted butter, stir in 1/2 cup of brown sugar, and pour this mixture into a greased 9-inch round cake pan. Arrange the peach slices over the mixture.
3-In a large mixing bowl, cream together: In a large mixing bowl, cream together 1/2 cup softened butter and 1 cup granulated sugar until light and fluffy. Add eggs one at a time, mixing well, then add milk and vanilla extract.
4-In another bowl, whisk together 1 ½: In another bowl, whisk together 1 ½ cups flour, 2 teaspoons baking powder, and 1/4 teaspoon salt. Gradually add this to the wet ingredients and mix until just incorporated.
5-Pour the batter over the arranged peach: Pour the batter over the arranged peach slices in the cake pan and smooth it out. Bake in a preheated oven at 350°F (175°C) for 35-40 minutes.
6-Allow it to cool for about 10: Allow it to cool for about 10 minutes, then carefully invert onto a serving platter.