Pineapple-coconut-banana Upside-down Cake

Why I Love This Recipe
Upside-down cakes are classically made in a cast-iron skillet because it gives the cake a crisp edge, cooks it evenly, and keeps it moist.
Ingredients You'll Need
2 tablespoons butter
3/4 cup packed brown sugar
1 (15 1/2-ounce) can pineapple slices in juice, undrained
1 cup flaked sweetened coconut
1 cup all-purpose flour
1/2 cup granulated sugar
1 teaspoon baking powder
1/2 teaspoon baking soda
1/2 teaspoon ground cinnamon
1/4 teaspoon salt
1/2 cup mashed ripe banana (about 1 banana)
2 tablespoons vegetable oil
1 large egg
Directions
Preheat oven to 375°.
Melt butter in a 9-inch cast-iron skillet; sprinkle evenly with brown sugar. Drain pineapple slices over a bowl, reserving 1/2 cup juice. Place 1 pineapple ring in center of skillet. Cut remaining pineapple rings in half; arrange around center pineapple ring. Sprinkle evenly with coconut. Set aside.
Lightly spoon flour into a dry measuring cup, and level with a knife. Combine flour and next 5 ingredients (flour through salt) in a large bowl. Combine reserved juice, banana, oil, and egg, stirring with a whisk. Add pineapple juice mixture to flour mixture, stirring until combined. Pour flour mixture over coconut. Bake at 375° for 30 minutes or until a wooden pick inserted in center comes out clean. Invert onto a wire rack. Serve warm or at room temperature.