Place butter in pan or pie plate and put in the oven. Preheat the oven to 350 degrees, allowing the butter to melt in the pan while warming.
Remove the pan from the oven once the butter has melted. Stir in brown sugar (you can do this right in the pan!).
Arrange pineapple slices and cherries on top of the butter mixture, as much or as little as you like.
Cake
In a medium bowl, whisk together oil and sugar.
Add applesauce, egg, and vanilla and whisk until combined.
Add flour, baking powder, baking soda and salt and stir just until combined. Spread carefully over pineapple in pan, making sure not to disturb the cherries as you spread the batter.
Bake for 20-25 minutes, until top of the cake is golden brown. Let cool for 5 minutes in the pan before running a knife carefully around the edge.
Place a large round plate on top of the pan, flip and allow the cake to fall out onto the plate before removing the pan.