Preheat oven to 180 degrees. Grease and flour a 13x9 inch pan and set aside.
Sift together the floor, baking soda, cinnamon and salt and set aside.
In a bowl, beat the butter and sugars till light and fluffy. Add one egg at a time and beat.
Add the vanilla and banana and beat.
Add half the flour mixture and the yogurt. Fold in well.
Add the remaining flour mixture and fold till batter is all moist and there are no lumps.
Spread into the pan and bake for 25-30 minutes till the skewer comes out clean in the center.
Cool completely before frosting.
To make frosting, beat all ingredients till well combined and light. Spread over the cooled cake.
Slice and enjoy!