Preheat oven to 400°F.
Place 4 tablespoons melted butter in 9-inch cake pan and tilt the pan back and forth to coat the bottom. Sprinkle the brown sugar evenly over the melted butter.
Arrange pineapple slices over brown sugar mixture; sprinkle with pineapple juice.
In large bowl, stir together flour, baking powder, salt and sugar. Add milk, egg, vanilla and remaining melted butter; beat until blended. Carefully spoon batter over pineapple in pan.
Bake 25 to 30 minutes, or until golden brown. Cool in pan on wire rack for 10 minutes. Turn out on serving plate; serve warm or cool.
Fresh pineapple or 1 (20 oz.) can pineapple slices may be used. If using canned pineapple, reserve liquid for pineapple juice.