Cream together the sugar butter, eggs and banana. Add the buttermilk, banana extract and oil. Mix well.
In a separate bowl, sift together the all-purpose flour, baking powder and salt.
Using a spatula and gently mixing by hand, add the flour mixture to the wet ingredients a little at a time, mixing until just combined after each addition. The batter should be smooth and completely combined, but avoid over mixing.
Pour into prepared (greased and floured) 9x13 inch baking pan. Bake at 350°F, for 35-40 minutes or until a toothpick inserted into the center comes out clean.
Allow to cool completely before frosting.
To Assemble and Decorate:
Spread Strawberry frosting across cake once completely cooled.
Slice bananas and toss to coat in lemon juice (to keep them from browning quickly.)
Place banana slices, pineapple tidbits and maraschino cherries on top of cake. Sprinkle walnuts across cake. Drizzle chocolate sauce across entire cake.