The most extraordinary moist caramelized Peach Upside-Down Cake made by preheating oven to 350°F melting 3 tbsp butter in oven-safe 9 or 10-inch skillet over medium heat adding 3/4 cup packed brown sugar stirring until smooth caramel forms removing from heat arranging 3 to 4 peeled sliced peaches in fan pattern over caramel whisking 1 1/2 cups flour 1 1/2 tsp baking powder and 1/4 tsp salt beating 1/2 cup softened butter and 1 cup sugar 2 to 3 minutes adding 2 room temperature eggs one at a time then vanilla alternately adding flour mixture and 1/2 cup sour cream beginning and ending with flour mixing just combined spooning batter carefully over peaches spreading gently to edges baking 35 to 40 minutes until toothpick clean cooling exactly 10 minutes running knife around edge and inverting confidently onto serving plate. A completely perfect caramelized brown sugar summer peach upside-down cake recipe.