Heat oven to 350 degrees. Grease 9-inch round springform pan. Pour melted butter into bottom of prepared pan. Sprinkle brown sugar evenly over butter; do not stir. Starting from outside rim, place concentric circles of peaches to cover bottom of pan. Set aside. Beat 1/2 cup butter and sugar in bowl of electric mixer on high until light and fluffy. Add eggs, one at a time, beating after each addition. Mix in vanilla extract. In separate bowl, whisk together flour, cornmeal, baking powder, salt, and lemon zest. Alternate additions of flour mixture and ricotta, folding into butter mixture after each addition until ingredients are just combined. Do not overmix. Batter will be thick. Carefully spoon batter into prepared pan, covering peaches and smoothing cake surface with spatula. Bake 45 minutes, or until knife inserted in center of cake comes out clean. Cool in pan for 20 minutes. Invert cake over plate or platter. Release and carefully remove springform pan. Serve cake warm.