At the risk of offending my Irish friends who find the manner in which we Americans celebrate St. Patrick's Day a tad offensive (leprechauns!  rainbows!  green beer!), I'm going to suffer their wrath and give you my contribution to our March 17th festivities:  A Double Rainbow Cake, dammit.

I have a smooth, round bundt pan, which makes this process rather simple but you can use a more sculptural bundt if that's all you've got lying around the house.

You may ask, where's the double in this rainbow.  Well, the second one is on the inside because that's where it really counts.

Happy St. Patrick's Day, sweet people!


for the cake

7 ounces cake flour
7 ounces superfine sugar
1/2 teaspoon salt
2 teaspoons baking powder
4 ounces unsalted butter, room temperature, cut into small pieces
3 large egg whites, room temperature
1 large whole egg, room temperature
6 ounces buttermilk
1 teaspoon vanilla extract
gel dye in red, orange, yellow, green, blue and violet

for the buttercream

3 egg whites
1/2 cup plus 2 tablespoons granulated sugar
1 teaspoon vanilla
8 ounces unsalted butter, room temperature

1 1/2 pounds plain, white fondant

for the cake

Preheat oven to 350ºF.  Spray a smooth bundt pan with non-stick baking spray.  Set aside.

In the bowl of a stand mixer fitted with the paddle attachment, combine the flour, sugar, salt, and baking powder.  Stir to combined.  Add the butter and mix until the mixture looks like wet sand.

Add the egg whites, one at a time, and then the whole egg, mixing between each addition.  The mixture should look like smooth paste.

Stir together the buttermilk and the vanilla and add in three additions, mixing on medium speed between each addition.

Divide the batter evenly between 6 bowls.  Add 2 drops of dye to each of the bowl to get the 6 colors.

Spoon the red batter into the pan, all the way around.  Add the orange on top of the red, being careful not to press down on the batters.  Continue layering the colors until they're all added.  It's easier to transfer the batter(s) to separate piping bags and pipe them, one on top of the other, but that's a lot of piping bags and it doesn't have to be perfect.

Bake for 35-40 minutes or until a toothpick comes out clean and the cake springs back when gently poked.  Allow to cool completely.

Once cool, cut the cake evenly in half.

for the buttercream

In the bowl of a stand mixer fitted with the whisk attachment, add the egg whites and sugar.  Whisk over a pan of simmering water until the sugar has melted and the mixture is hot (it should reach 160ºF).  Transfer to the mixer and whisk until the meringue reaches stiff peaks and the bowl is cool to the touch.  Add the vanilla and whisk to combine.

Add the butter, a few pieces at a time, whisking well between additions.  Continue adding the butter until the mixture thickens and then smooths out.  It will look broken just before coming together.  You may not need all the butter.

Spread a few tablespoons of buttercream on one flat side of the cut cake and place the second cake half on top.  Press to adhere the two together and stand the now combined halves so that the cake is "standing" like an arch.  Spread a thin crumb coat over the cake and refrigerate to firm.

Transfer the remaining buttercream to a piping bag fitted with a large, plain tip and set aside.

to finish

Divide the fondant into 6 even pieces.  Add a few drops of dye to each piece, one red, another orange, another yellow, another green, then blue and violet.  Knead the dye into the fondant until the color is evenly distributed.  At the moment, my hands are riddled with colorful splotches so it behooves me to recommend that you wear latex gloves when you do this.

Roll each piece into a 10-12 inch rope and place the pieces next to each other, leaving a slight gap between each.  Roll out the pieces until somewhat flat and then slightly moisten the sides of each pieces (not the top or bottom) and continue rolling until the pieces are touching and the fondant is about 1/8" thick.  The entire piece should be about 18" x 10", more or less.

Transfer the piece on top of the arch and gently smooth the fondant with your hands over and around the arch, gently stretching as you go along for optimal coverage.  Trim any errant pieces at the base.  Pipe the remaining buttercream in small, cloud-like blogs along the base of the rainbow.

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