Place 2 TBLS margarine in 9 X 1 1/2" round micro baking dish. Microwave on High (100%) until melted, 30 to 45 seconds. Stir in 1/4 cup brown sugar; spread evenly in dish. Arrange pineapple slices and cherries over brown sugar. Mix Jiffy cake mix according to pkg directions and pour over pineapple. Microwave at MEDIUM-HIGH (70%) for 4 mins. Increase power to HIGH (100%). Microwave until woodein pick inserted in center comes out clean, 5-8 mins. Cool 2 mins, and invert on plate.