Preheat oven to 350 degrees F. Coat two 8-inch cake pans with cooking spray. In a large bowl, cream the granulated sugar and shortening until light and fluffy. Add eggs and beat thoroughly. Gradually blend in baking soda, flour,and salt. Beat in mashed banana and 1 teaspoon vanilla until thoroughly combined. Pour mixture into prepared cake pans.
Bake 25-30 minutes,or until a wooden toothpick inserted in center comes out clean. Let sit 5 minutes,then remove cakes from pans and place on a wire rack to cool. In another bowl,combine cream cheese,peanut butter,and butter. Beat until fluffy. Add confectioners' sugar and remaining vanilla. Beat until thoroughly combined. Frost cake and sprinkle with peanuts.