Preheat oven to 350° F.
Pour melted margarine into an 8-inch square baking pan.
Sprinkle with brown sugar.
Spread crushed pineapple evenly oh bottom of pan.
In a mixing bowl, sift together flour and white sugar.
Add oil and 1/4 cup of the milk.
Stir until flour is dampened, then beat 1 minute.
Stir in baking powder, remaining milk, egg whites and vanilla.
Beat 2 minutes.
Pour batter over crushed pineapple in cake pan.
Bake 35 to 40 minutes, or until a toothpick inserted in center comes out clean.
Remove from oven, cool slightly and invert onto a serving plate.