Nectarine, Plum, and Apricot Upside-Down Cakes - Master recipes

Ingredients

• 1 c. unsalted butter -
• 3 tbsp. maple syrup -
• 1 tsp. dark rum -
• 2 c. light brown sugar -
• 1/2 tsp. vanilla extract -
• 1/2 tsp. Coarse salt -
• 2 1/2 lb. nectarines, plums, or apricots -
• 1 1/2 c. all-purpose flour -
• 1 1/2 c. cake flour -
• 1 tbsp. baking powder -
• 1 tsp. salt -
• 1 3/4 c. sugar -
• 4 large eggs -
• 2 tsp. pure vanilla extract -
• 1 1/4 c. milk -