Preheat oven, prepare pan, and combine dry ingredients: Preheat oven to 350°F. Spray a 9-inch round cake pan with oil. In a medium bowl, whisk together flour, baking powder, and salt.
Combine dry ingredients: In another medium bowl, whisk together ⅔ cup sugar, honey, eggs, melted butter, and milk.
Whisk wet with dry ingredients: Whisk egg mixture into flour mixture until just combined.
Make caramel: In a small, heavy saucepan over high heat, combine remaining ⅔ cup sugar and 3 tablespoons water. Cook, swirling pan occasionally (do not stir), until mixture is deep amber, about 5 minutes. Remove from heat; stir in room-temperature butter. Immediately pour into prepared pan.
Arrange apples and spread batter: Decoratively arrange layers of apples over caramel filling. Spread batter evenly over apples.
Bake: Bake until top springs back when lightly touched, 45 to 55 minutes. Loosen edges with a knife. Let stand 5 minutes before inverting onto a serving plate. Serve warm or at room temperature.
