Chocolate Rainbow Cake
A rich chocolate bundt cake with a tight, dense crumb and a gorgeous rainbow surprise inside!

- Prep time
- 30 min
- Cook time
- 1 hr
- Yield
- 12 servings
- Difficulty
- HARD
Ingredients
Quantities are shown as originally provided.
- 226 g unsalted butter
- 75 g refined coconut oil ( melted or solid)
- 400 g granulated sugar
- 1 tsp fine sea salt
- 2 tsps baking powder
- 2 teaspoon pure vanilla extract
- 4 large egg whites plus 1 egg yolk
- 360 g cake flour
- 250 g plain kefir or buttermilk (plus another 20g)
- 40 g dutch process or black cocoa
- 1 cup powdered sugar (130g)
- ¼ cup dutch process cocoa
- ¼ cup milk (more as needed)
- Pinch fine sea salt
- 1 tsp pure vanilla extract
Instructions
- 1
Preheat oven to 350 F. Butter and flour a large bundt pan.
- 2
Cream butter, coconut oil, sugar, salt, vanillas and baking powder for a full 5 minutes until very light and fluffy.
- 3
With the mixer on, add egg whites, one at a time allowing each to be fully incorporated before adding another.
- 4
Add the sifted flour mixture then turn the mixer on low and slowly drizzle in the buttermilk.
- 5
In 5 separate bowls, add 1/3 cup of batter. Using gel food coloring add red, yellow, green, blue and purple to each bowl and stir to combine the colors.
- 6
To the remaining batter add the cocoa, egg yolk and additional buttermilk. Mix to combine.
- 7
Use most of the cocoa batter to fill your bundt pan. Leave the last bit for the top, to cover the rainbow.
- 8
Place each of the colored batters in a piping bag (you'll have five) and snip off the top. Use the back of a teaspoon to create a moat in the chocolate batter.
- 9
Pipe a red circle into the moat then use the back of a spoon to smooth it out so that it's as wide as possible while still leaving a white border on the inner and outer rim.
- 10
Now add the yellow, leaving a red border on either side. Each following color will decrease in width - see photos above. Spoon the rest of the chocolate batter on top with an offset spatula, careful not to smoosh the rainbow.
- 11
Bake for 45 minutes, checking for doneness at 40. The bundt is done when you can touch it and it springs back.
- 12
Allow cake to cool in pan for about 15 minutes, then invert onto a cooling rack.