Gather all ingredients. Preheat the oven to 350 degrees F (175 degrees C).

Drain canned pineapple into a 1-cup measure. Add water if needed to measure 1 cup. Set aside juice and 9 pineapple rings for the cake. Set any remaining juice and pineapple rings aside for another use.

Melt butter in a 12-inch cast iron skillet over medium-high heat.

While butter is melting, combine cake mix, reserved 1 cup pineapple juice, vegetable oil, and egg whites in a mixing bowl. Beat with an electric mixer on medium speed for 2 minutes.

Remove melted butter from the heat and sprinkle brown sugar evenly over top until all the butter is covered. Arrange 8 pineapple rings around the outer edge of the skillet and place the remaining pineapple ring in the center without overlapping. Place a maraschino cherry into the center of each pineapple ring; pour cake batter on top.

Bake in the preheated oven until a toothpick inserted into the cake comes out clean, about 40 minutes.

Remove from the oven and let cool in the skillet for 10 minutes; don't let the cake cool too much or it will stick to the pan.