Preheat the oven to 330 F. Line one or two cupcake trays with 16 paper cases. Sift together the flour, cocoa powder, baking soda, baking powder and salt and set aside.
Put the eggs, sugar, and vanilla extract into a mining bowl and beat on medium speed for 5 minutes. Scrape the inside of the bowl with a rubber spatula and beat for another 5 minutes, now on high speed. Scrape the inside of the bowl again, add the mayo and beat until blended into the mixture. Sift in the flour mixture in two addition alternating with the water and stir until everything is well blended. Divide the mixture between the paper cases, and bake on the middle rack for 20-25 minutes, or until a cake tester comes out clean. Transfer to a wire rack to cool.
Frost using your choice of frosting, top with some sprinkles or fresh fruit and serve!