This recipe is from Taste of Home and is very tasty......and easy:
Banana Snack Cake
1/2c shortening
3/4c packed brown sugar
1/2c sugar
2eggs
1c mashed bananas (2-3 med)
1 tsp vanilla
2c flour
1 tsp baking soda
1/2c buttermilk
1/2c chopped nuts
Frosting:
1/2c brown sugar
1/4c butter
6T milk
2 1/2-3c conf. sugar
Mix shortening and sugars. Add eggs one at a time
beating well after each. Add bananas and vanilla.Combine
dry ingredients and add alternately with buttermilk.
Stir in nuts and spread in a greased 9x13" pan.
Bake at 350° for 25-30 minutes til tests done.
Cool and frost:
Combine in a small saucepan brown sugar,
butter, and milk. Boil and stir for 2 minutes.
Cool to lukewarm and add conf. sugar until
of spreading consistency. Frost cooled cake
12 servings.

Hope this isn't too late for you. This is a recipe that I started making years ago because of it's low fat content. The bars are slightly on the 'tough' side, but not at all objectional. Always liked wherever I took them.

Banana Bars
1/4 cup shortening
1 cup sugar
2 eggs
1 cup mashed very ripe banans
1 tsp. vanilla
2 cups flour
2 tsp. baking powder
1/2 tsp salt

Mix shortening, sugar, eggs, bananas, and vanilla
thoroughly. Blend dry ingredients together. Stir into banana mixture. Spread into greased jelly roll pan. Bake at 350 for 20 to 25 minutes.
Frost cooled bars with a thin layer of frosting of your choice. I always used a vanilla powdered sugar with butter icing.

what about Banana Crumb Cake?

Banana Crumb Cake

2C sugar
1 C milk
1 C chopped nuts (optional)
2 C self rising flour
1 stick margarine
2 eggs
3 Bananas
1 tsp vanilla

Crumb Topping
1 stick (1/2 c) Margarine
1 Cup brown sugar (dark or light)
1 cup flour (self rising or plain, whatever you have on hand)

Spray two loaf or 8Ã8 pans with cooking spray. Place peeled bananas in mixing bowl, add sugar. Mix until bananas are liquefied. Add margarine, mix until creamed together with banana mixture. Add all other ingredients and blend well.

In medium bowl, place all topping ingredients. Cut together with a long tined fork until well blended. Pour 1/4 of batter into each pan, top with 1/4 crumb mixture. Pour remaining batter over and top with remaining crumb mixture. Bake for 45 minutes to an hour at 350.

Cake is done when toothpick inserted in center comes out clean.