Cream together sugar and margarine.  Add eggs and sour cream; mix well. Add bananas and vanilla. Stir together salt, soda and flour; add to banana mixture; mix well.

Spread dough in a greased and floured 15 x 10 inch pan.

Bake in a 350 oven 20-25 minutes. 

Cool and spread with the following: Melt ¼ cup margarine  in pan over low heat until bubbly.  Remove from heat. 

Add 2 cups sugar and 3 T sour cream.  Beat with a mixer until creamy. 

Spread on baked mixture.  

When cool, cut into bars.