secret recipe club: whole wheat grapefruit cake

this is the first time, in the nine months i've been participating in the secret recipe club that the initial recipe i chose didn't work out for me. i'm sorry sarah, as good as your chocolate snacking cake looked, as simple as it appeared, i somehow managed to tinker with it a wee bit too much. let me be honest: it's my fault. the cake came together wonderfully, the batter tasted great, and i decided, for whatever reason, to mix in chocolate and peanut butter chips and bake it in two loaf pans instead of a square pan. that's where it went wrong. the cakes sunk, the chips fell to the bottom, and both cakes stuck like crazy to the pan. but even with all that, it's on my short list to remake, because the chunks i've been gobbling up the last couple days taste amazing. even if it isn't too pretty.

and that chocolate cake is a long winded way to bring me to this whole wheat grapefruit cake from sarah at simply cooked. i don't cook much with grapefruit (have i ever eaten one? i don't think so. that has to be some kind of food crime in and of itself.), which is somewhat surprising since i love the sweet tart flavor almost as much as the hubs loves lemon. so this cake - marked as my back up, in case the chocolate let me down - stole the show. the whole wheat flour results in more of a coarse and ever so slightly dense cake than light and fluffy. which is fine by me, since it goes great with the zesty grapefruit in the cake. and this time, i learned my lesson: i didn't stray a bit from sarah's recipe. at least for the cake. where sarah topped hers with a grapefruit glaze, i opted for grapefruit spiked buttercream. it's the perfect, light pink, sweet tart icing on the cake. this one's a keeper, for sure.

for more information on the secret recipe club, including the list of participating bloggers, featured recipes from members, and instructions on how to join, visit the secret recipe club website!

check out my previous secret recipe club posts below
chewy no bake granola bars & carrot cinnamon waffles
cannoli
gingerbread muffins
double chocolate peanut butter chip oatmeal cookies
butterscotch peach cake
whole wheat honey pancakes minted pineapple lime agua frescabreakfast tacos
simple almond sandwich cookies
roasted banana rum cake

whole wheat grapefruit cake
adapted from simply cooked
1 hour plus cooling, makes one 8x8" or 9x9" cake

for the cake and buttercream, you will need 1 cup grapefruit juice and 2 tablespoons of zest. for me, two large grapefruits yielded about 1 1/2 cups juice and a ton of zest. drink the remaining juice and find a good use for the extra zest!

for the cake:
2 large grapefruits, juiced and zested
5 eggs, separated
1/2 cup vegetable oil
1 1/2 cups sugar
2 cups whole wheat flour
2 teaspoons baking powder
1/2 teaspoon salt
1/4 teaspoon cream of tartar

for the grapefruit buttercream:
1/2 cup fresh grapefruit juice
6 tablespoons unsalted butter, room temperature
1 1/2 cups powdered sugar

1. make the cake. preheat your oven to 350F. line a 8x8" or 9x9" with a parchment paper sling. set aside.
2. in a medium bowl, beat the egg whites until they are soft peaks. mix in the cream of tartar.
3. in a separate bowl, beat the egg yolks with the vegetable oil until combined. mix in the sugar until smooth and pale. the mixture will be thick, but it will still get lighter in color as you mix it. mix in 1/2 cup grapefruit juice and 2 tablespoons grapefruit zest.
4. add the flour, baking powder, and salt to the egg yolk mixture and mix until combined.
5. fold the egg whites into the egg yolk mixture in three additions. be careful not to deflate the whites.
6. pour into your prepared pan and bake for 30 to 40 minutes, or until a toothpick comes out clean. let cool in the pan for about 15 minutes before lifting out by the parchment sling onto a wire rack. cool completely before icing.
7. while the cake is baking & cooling, make the buttercream. in a small pan, simmer the grapefruit juice until it is reduced to about half the volume. this should take about 5 minutes. don't worry if you see foam on the surface, you can skim it off or leave it in as it will dissolve with the juice when it cools. once reduced, let cool to room temperature.
8. mix the cooled juice, butter, and powdered sugar until smooth.
9. when the cake is cool, spread with grapefruit buttercream. store in an airtight container.