1.Combine the melted butter, brown sugar, and cinnamon. Pour into a 9-inch cake pan. 2.Top the mixture with the sliced peaches. 3.In a medium bowl, whisk together the flour, baking powder, and salt. 4.In a separate bowl, beat together the butter and sugar until light and fluffy. Add the vanilla and egg yolks. 5.Add half the flour mixture to the butter mixture and beat until combined. Add the milk and beat again. Pour the remaining flour mixture into the bowl and mix until combined. 6.In a separate bowl, combine the egg whites and cream of tartar. Beat the mixture on high speed until stiff. Pour the mixture into the batter and fold in. 7.Pour the batter over the peaches and spread evenly. 8.Bake in the preheated oven for 45 minutes. 9.Allow to cool slightly, then run a knife around the edge of the pan to loosen the cake. Flip the pan over onto a serving plate. Serve warm or at room temperature.