Preheat oven to 350 F (180 C). Put the 2tbsp butter in a 9 round pan and put pan in the oven while preheating to melt the butter. Remove from oven and stir in the brown sugar and water.
Arrange pineapple slices over top and place a halved cherry, cut side down, in the centre of each slice.
In a medium bowl, mix together flour, sugar and baking powder.
In a large mixer bowl, combine egg, milk, butter and vanilla, beating on low speed until blended. Beat in flour mixture on medium speed for 2 to 3 minutes, until thoroughly combined. Spoon into baking pan over the fruit, spreading evenly.
Bake in preheated oven for 30 to 35 minutes or until a toothpick inserted in the centre comes out clean and dry. Let cool in pan on a wire rack for 5 to 10 minutes, loosen around the side with a knife and then invert onto a serving plate. Best when served slightly warm.