Beat the butter and mayonnaise in the bowl of a stand mixer fitted with the paddle attachment, on high, until light and fluffy, 3 to 4 minutes. With the mixer on low, slowly add the melted chocolate. Continue mixing on low speed until all of the chocolate is incorporated, stopping to scrape down the sides of the bowl as needed.
In large bowl, beat granulated sugar and 3/4 cup softened butter with electric mixer on medium speed until light and fluffy, scraping bowl occasionally. Beat in 1 1/2 teaspoons vanilla and eggs until well blended.
A moist yellow cake that's better than a box mix, Alton Brown's reloaded gold cake is sweet, tender, & best frosted with cocoa whipped cream. Way back in 2003, I created a yellow cake that was dry, crumbly, and not nearly the cake the world deserves. After all these years I can finally say: we’re golden...cake that is.
Use a hand mixer or stand mixer to prepare the batter, bake in a prepared cake pan (see next section for cake pan sizing), and cool until you’re ready to frost. I’ve made this keto yellow cake into a sheet cake with a 9×13 pan, cupcakes, and as a layer cake using an 8″ or 9″ round pan.