Rainbow Chocolate Cake

Part cake, part giant oatmeal cookie, this colorful bake is topped with M&M’s that sink into the batter and create a rainbow mosaic on top. Kids go absolutely wild for it, and the recipe is simple enough that they can help make it too.

The batter is more cookie than cake: butter creamed with brown sugar and white sugar, then mixed with oats, flour, cinnamon, and chopped nuts. It bakes up dense and chewy, not light and fluffy, with those candy-coated chocolates scattered across the top melting just enough to stick while keeping their crunch.

Brown sugar does most of the sweetening here, which gives the cake a caramel-toffee depth that pairs well with the chocolate candies. The cinnamon is subtle but adds a warm note in the background that makes each bite more interesting than just sweet.

Pro Tips

• Spread the thick batter evenly in the pans; uneven spots will overbake on the thin edges
• Press the M&M’s gently into the top of the batter so they stay put during baking
• Cool in the pans for a full 10 minutes before transferring; these are fragile when hot
• Cut into squares or wedges and serve from the pan for a more casual presentation

Variations

• Use Reese’s Pieces instead of M&M’s for a peanut butter-chocolate combo
• Add chocolate chips to the batter along with the M&M’s on top for extra chocolate
• Skip the nuts for a nut-free version that’s school-lunch friendly