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This blueberry sheet Cake is one of those recipes you make once and then just keep making. It’s packed with fresh blueberry and bright Lemon flavor, baked in a simple 9×13 pan, and finished with the most gorgeous blueberrycream cheese frosting you’ve ever seen. That lavenderpurple color will stop people in their tracks — and the flavor will make them come back for a second slice before they’ve finished the first.
Why You’ll Love It
No fussy layers — it’s a 9×13, which means no leveling, no stacking, no special carrier. Just a pan with foil and you’re out the door. Real blueberrylemon flavor — the zest, the juice, and the fresh berries in the batter all work together. It tastes bright, not just sweet. That frosting — blueberry jam whipped into cream cheese and butter. The color alone is worth making this cake for. Crowdfriendly and forgiving — feeds a group easily and holds up well, which is more than you can say for most layer cakes. You’ll make it more than once — this is the kind of recipe that quietly becomes your goto.
A Few Notes on the Ingredients
The buttermilk is nonnegotiable in my mind. I know some people do the vinegarinmilk trick and it’s probably fine but I always have buttermilk on hand because I make pancakes too often and I’d rather just use the real thing. Make sure it’s room temperature — cold buttermilk will seize up your batter and you’ll wonder what went wrong.
The blueberries: fresh, please. I’ve tried this with frozen and it works, technically, but the berries bleed into the batter in a way that changes the texture. If it’s not blueberry season and fresh ones are sad at the store, I’d honestly just wait. This cake deserves good berries.
Lemon zest — zest three lemons and don’t skimp. I know it sounds like a lot. It’s not a lot. That brightness is what makes the cake taste alive instead of just sweet.
For the frosting, the blueberry jam is the magic. I use a good one, something with real fruit and not too much corn syrup. The brand doesn’t matter as much as the quality. I’ve used homemade jam when I had it and it’s incredible, but storebought totally works.
Ingredients
For the cake: 3 cups allpurpose flour, plus 1 tablespoon set aside for the berries 2 teaspoons baking powder 1 teaspoon baking soda ½ teaspoon salt 1 cup (2 sticks) unsalted butter, softened — really softened, not just slightly less cold 1½ cups granulated sugar 4 eggs, room temperature 2 teaspoons vanilla extract 1 cup buttermilk, room temperature Zest of 3 lemons (I eyeball this — be generous) ¼ cup fresh lemon juice, about 2 lemons 1½ heaping cups fresh blueberries
For the frosting: ¾ cup unsalted butter 6 oz cream cheese, room temperature — this matters, don’t rush it ¼ cup blueberry jam 3 cups powdered sugar 1 teaspoon vanilla
Let’s Make It
Preheat your oven to 350°F and get your 9×13 ready. I grease mine well and also line it with parchment when I’m planning to serve it at something — if I’m just leaving it in the pan for the family to pick at, I skip the parchment. Either way is fine.
Whisk your dry ingredients together in a bowl and set them aside. In your stand mixer — or a big bowl with a hand mixer, I’ve done it both ways — cream the butter and sugar until it’s genuinely light and fluffy. This takes longer than you think. Give it a real 23 minutes. Add the eggs one at a time, then the vanilla, and mix until combined. Pour in the buttermilk slowly with the mixer on low. The batter might look a little curdled at this stage and that’s okay, it comes together.
Add the dry ingredients in two additions — don’t dump it all in at once, I’ve done that when I’m in a hurry and the flour goes everywhere — and mix until just combined. Then add your lemon juice and zest. Toss the blueberries with that reserved tablespoon of flour first. This is one of those steps that feels fussy but it genuinely helps keep the berries suspended in the batter instead of sinking. Fold them in gently.
Pour into your pan and bake for 4045 minutes. Mine usually needs the full 45, sometimes a minute or two more — ovens vary wildly, mine runs a little cool, I’ve never fully trusted it since we moved and I keep meaning to get an oven thermometer and forgetting. Check it with a toothpick in the center. Let it cool completely before frosting. Completely. Do not rush this. A warm cake will melt your frosting and you’ll be sad.
While it cools, make the frosting. Whip the butter in a mixing bowl until it’s pale and fluffy — this takes a good 58 minutes and it’s worth it, don’t stop early. Add the cream cheese and beat until it’s fully incorporated and smooth. Mix in the jam. Then add the powdered sugar a little at a time on low — if you dump it in fast you’ll be covered in a cloud of sugar, ask me how I know — and once it’s all in, add the vanilla and crank the speed up and whip for another couple minutes until it’s light and beautiful and that color. That gorgeous, improbable color.
Spread it over the cooled cake. I use an offset spatula and make swirly swoops. You could scatter a few fresh blueberries on top for looks, though I don’t always bother.
Variations
You can swap the blueberries for raspberries and use raspberry jam in the frosting — the pink is even more dramatic. I once tried making it with blackberries because that’s what I had and it was delicious but the frosting turned a color that I can only describe as grayishpurple, which tasted incredible but looked a little alarming. If you’re taking this somewhere, stick with blueberry.
You could do this with a lemon curd swirl in the batter instead of the juice, though I haven’t tried it myself. Someone in the comments on some food site suggested it once and I’ve been meaning to experiment. One of these days.
Keeping It
The cake keeps fine on the counter, loosely covered, for about two days. After that I’d refrigerate it — the cream cheese in the frosting makes me nervous past 48 hours unrefrigerated, though honestly I’ve never had a piece last that long without disappearing. From the fridge it’ll keep for four or five days. Let it come to room temperature before eating if you can — cold cake is okay but roomtemperature cake is the version that made you fall in love with it in the first place.
I don’t freeze it. I’ve heard of people freezing frosted cake slices and I respect the ambition but I’ve never done it with this one. Seems like it would change something.
One more thing — the lemon flavor in this cake is bright without being puckery. It works with the blueberry instead of competing with it, which is exactly what you want.
Slice it into whatever size you want. I cut mine smaller than I probably should and then go back for another piece, which I think is the correct way to eat a sheet cake anyway.