Heat the oven to 400° F. Butter and flour a 9- or 10-inch springform pan.
Cream the butter, sugar, and lemon zest in a standing mixer until light and fluffy, scraping down with a rubber spatula as needed.
On the lowest speed, add the eggs one at a time, scraping down as needed.
Still on low speed, add the peaches, then the baking powder and salt. Mix until combined.
Alternate between adding the flour and ricotta, scraping down as needed.
Add the batter to the prepared pan, smooth the top and bake for about 30 minutes, until the cake is deeply browned and the sides start to pull away from the pan. (If it starts to brown too swiftly, you can cover the top with foil mid-bake.)
Cool in the pan on a wire rack for 10 minutes. Remove the cake from the pan and cool completely on the rack.
Sift confectioners' sugar over the top just before serving.