Procedure
Preheat the oven to 347°F. In a medium-sized bowl, sift together all-purpose flour, baking powder, baking soda, and salt. In another bowl, add sugar and shortening, and blend them to make a fluffy and light mixture. Beating with every addition, add one egg at a time, into this mixture. Then put in the mashed bananas and mayonnaise and blend the mixture properly.