Broiled Grapefruit Sheet Cake

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Everybody loves a sheetcake. It’s a simple, no-fuss, humble dessert fit for a dinner party, or a Tuesday. This version starts with broiled grapefruit juice that gives it a subtle citrus flavor perfect for summer. Have you ever broiled a grapefruit?! Trust me on this, guys!! It’s heaven – The sugars carmelize and bring out the natural sweetness and it’s honestly the only way I care to eat grapefruit these days.

The cake is baked up in a 9″ square cake pan and topped off with lime buttercream. This cake is delicious. So delicious that I had to give it to the neighbors to stop myself from eating the whole pan. And if you STILL aren’t convinced – my brother who DOESN’T EVEN LIKE CAKE – said it’s awesome. So, yeah. I love citrus flavored everything in the summer time. And as much as I love lemon – grapefruit is a fun twist.

But if you are looking for a great lemon dessert – my soft sugar cookies with lemon cream cheese frosting will hit the spot. Check them out here.

How to Make Broiled Grapefruit Sheet Cake

Broil the Grapefruit

*** You will need the zest of the grapefruit for the cake batter as well. It is much easier to zest the grapefruit BEFORE you broil it. ***

First you need to get that delicious caramelized grapefruit juice that makes this cake so special. If you’ve never broiled a grapefruit, you’re about to want to give me a huge hug – because it’s amazing. Just slice a grapefruit in half, sprinkle it with some granulated sugar, and stick it under the broiler. It only takes about 5-7 minutes – but watch it closely, because it’ll happen fast.

I like to get mine pretty charred so that the sugars in the juice get extra caramelized – like in the photo above. Once the grapefruit is cool enough to handle squeeze the juice and strain out the pulp. We want the flavor from the juice, but no one wants a soggy piece of pulp in their cake – well at least I don’t.

Make the Cake Batter

Preheat the oven to 350 degrees. Whisk the dry ingredients (flour, salt, baking powder) into a medium sized bowl and set aside. Stir the vanilla, grapefruit zest, grapefruit juice, and buttermilk together. Set aside.

In the bowl of a stand mixer fitted with the paddle attachment, cream the butter and sugar for about 3 minutes, or until it is light and fluffy. You want it to be similar to the texture of a fine sand. Next, mix in the eggs one at a time until incorporated

Now, add in 1/3 of the dry ingredients to the butter/sugar/egg mixture. Mix until just combined. Then add half of the buttermilk mixture, mix to combine. Repeat. Lastly, add in the final 1/3 of the dry ingredients. Mix until the flour is just combined, being careful not to overmix.

Baking the cake

Prepare a 9″ square cake pan (I like this one) by lining it with parchment paper and some nonstick spray. You can also use butter and a sprinkle of flour. I always leave an overhang of parchment so that it is easy to lift the cake out of the pan after it’s cooled.

Pour the batter into the prepared pan and smooth out the top with a rubber spatula. Bake for 45-50 minutes, or until a toothpick comes out with a few moist crumbs. Allow the cake to cool in the pan, then remove and allow to completely cool before frosting.

Make the Lime Buttercream Frosting

In the bowl of a stand mixer fitted with the whisk attachment, beat the butter for at least 5 minutes at medium high speed. 10 minutes is even better. You want the butter to become lighter in color and very smooth with no lumps – and the best way to do that is to beat it for a long time.

Next, add in the powdered sugar, 1 cup at a time. Add the vanilla, lime juice, lime zest, 2-3 TBSP of heavy cream, and a pinch of salt. I promise the salt won’t make your frosting salty – salt just brings out the flavor of everything else. Trust me.

Finally adjust to get the texture you want. If you want to thin the frosting out a little, add a little more cream. If you want it to be thicker, add some extra powdered sugar.

Frost the cake using an offset spatula, cut into squares, and enjoy.

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