Step #6 In a separate bowl, melted margarine, mix buttermilk, & vanilla.
Step #7 With mixer running at lowish speed, add flour mixture to egg mixture alternately with buttermilk mixture, beginning & ending with flour mixture.
Step #8 Pour batter into prepared pan.
Step #9 Bake 28 mins.
Step #10 Let cool in pan 10 mins on a wire rack; remove this from pan.
Step #11 Let cool completely on wire rack.
Step #12 Combine yogurt & brown sugar; stir well.
Step #13 Using a serrated knife, split cake in half horizontally.
Step #14 Place bottom layer, cut side up, on serving plate.
Step #15 Spread with half of yogurt mixture, top this with strawberries.
Step #16 Combine bananas & lemon juice & toss carefully.
Step #17 Drain bananas & discard juice.
Step #18 Arrange bananas over strawberries; drizzle with remaining yogurt mixture.
Step #19 Top with remaining layer.
Step #20 Sift powdered sugar over cake.
Step #21 Serve with whipped cream also, if desired.