Preheat the oven to 350°F (175°C).
Melt the butter and brown sugar together in a saucepan over medium heat.
Pour the butter and brown sugar mixture into a 9-inch round cake pan.
Arrange the pineapple slices and cherries on top of the caramel.
In a mixing bowl, combine the flour, baking powder, and salt.
In another bowl, cream the granulated sugar and remaining butter until light and fluffy.
Add eggs one at a time, mixing well after each addition.
Stir in the vanilla extract and milk until just combined.
Gradually add the dry mixture to the wet ingredients, mixing until just incorporated.
Pour the batter over the pineapple and caramel layer in the cake pan.
Bake for 40-45 minutes, or until a toothpick comes out clean.
Let the cake cool for 10 minutes before inverting onto a serving plate.
Serve warm or at room temperature.