High Altitude Lemon Blueberry Sheet Cake

A high altitude tested, lemon blueberry sheet cake, frosted with lemon and blueberry cream cheese buttercream in pretty piped florals. The lemon blueberry cake is moist and a little dense, full of plump blueberries and flavored with both fresh lemon zest and lemon juice. And today’s post also includes an easy photo tutorial for piping the beautiful buttercream flowers on top.

You might also love these high altitude sheet cake recipes for carrot cake, strawberry cake and chocolate cake.

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Why You’ll Love This Recipe

Smaller Size. Sheet cakes are usually made for a larger group, in a 9×13 baking pan, or sometimes even bigger. Today’s cake is a smaller, 8-inch one layer cake that serves 9 people. You can easily adjust the recipe for a larger cake, if that’s what you need.

Easy to Decorate. If you’re a beginner cake decorator, or just a little unsure of your skills, you’ll appreciate the ease and simplicity of today’s design. Using just one piping bag, one piping tip and a few easy techniques, you can create a beautiful buttercream floral design on your blueberry sheet cake.

Fresh Summer Flavors. This blueberry lemon cake is full of flavor from fresh blueberries and fresh lemon juice and zest. It’s as delicious to eat as it is pretty to look at.

High Altitude Tested. I develop all the recipes on my site for Denver’s altitude of 5,280 feet. If you’re at a lower or higher elevation, please see my FAQs for guidance on adjusting recipes for your altitude.

See the recipe card at the end of the post for the full ingredients list and instructions.

Ingredients

Cake

• Granulated Sugar. Adds sweetness and moisture.
• Lemons. You’ll be using both the zest and the juice for lots of fresh lemon flavor.
• Flour. For the softest texture, use cake flour, which has a lower protein content than all-purpose flour.
• Baking Powder. Leavens the cake so it rises as it bakes.
• Salt. Balances the sweetness.
• Eggs. Gives the cake structure and adds moisture.
• Sour Cream. Adds moisture and acidity for a tender cake crumb.
• Butter. Adds flavor, moisture and a rich buttery flavor.
• Vanilla Extract. Flavor.
• Blueberries. Use fresh blueberries, rather than frozen.

Buttercream

• Cream Cheese + Butter + Shortening. To make the most stable cream cheese buttercream for piping the flowers, you need to use a combination of cream cheese, unsalted butter and vegetable shortening. While it won’t have as much cream cheese flavor as cream cheese frosting that’s made with just cream cheese, it will hold its shape much better for piping. If you’re more interested in just the flavor and not in decorating your cake with piped buttercream, then you can make the frosting with half cream cheese and half butter, or just cream cheese, which will make a softer frosting. You can also cut the frosting recipe in half, if you plan on just spreading it on top of your cake.
• Powdered Sugar. Sweetens and thickens the buttercream.
• Meringue Powder + Corn Starch. A little of both these ingredients helps to stabilize and improve the texture of the buttercream.
• Lemon + Vanilla Extracts. Flavor.
• Freeze Dried Blueberry Powder. Adds natural color and blueberry flavor to the buttercream.

Instructions

Cake

• Preheat the oven to 350 F, and position a rack in the center of the oven. Lightly spray an 8-inch square baking pan with non-stick baking spray, or line with parchment paper.
• In a bowl, zest the lemon over the sugar, then use your fingers to rub the lemon zest into the sugar until moist and fragrant.

• Sift in the cake flour, baking powder and salt, then whisk together with the lemon sugar until evenly combined.
• Separately, whisk together the eggs, sour cream, melted butter, vanilla extract and lemon juice. Add the wet ingredients to the dry, and stir the batter together with a spatula, until there are just a few floury streaks left. Fold in the blueberries.

• Spread the batter evenly into the prepared pan, and bake for about 38-40 minutes, until a cake tester or toothpick comes out clean.
• Set the pan on a cooling rack and cool the cake completely before frosting.

Buttercream

• In the bowl of your stand mixer fitted with the paddle attachment, beat the cream cheese for 1 minute until smooth. Add the butter and shortening, and beat for another minute until smooth.
• In a separate bowl, combine the powdered sugar, meringue powder and corn starch. With the mixer on low, add the powdered sugar mixture by spoonfuls, mixing until combined. Add the lemon and vanilla extracts.
• Increase the speed to medium and whip for about 3-5 minutes, until light and fluffy, scraping the bowl down several times. Turn the speed down to “stir” and mix for 1 minute.

Decorating

• You can either frost and decorate just the top of the cake right in the pan, or turn it out onto a serving plate to frost the top and sides of the cake. Start by frosting the cake with a thin layer of the buttercream.

• Divide the remaining buttercream in half, and add the freeze dried blueberry powder to half the buttercream.

• Fit a 16-inch disposable piping bag with tip 1M. Fill the piping bag with the buttercream, alternating between spoonfuls of the lemon and the blueberry buttercream. By alternating the colors, they’ll blend together as you pipe the flowers for more variegation in color.
• Start by piping groups of rosettes on top of the cake.
• Then add a few ruffly mounds of buttercream. To do this, hold the piping bag perpendicular to the cake and twist the piping bag back and forth in 45-degree turns as you squeeze the buttercream out. These aren’t really flowers, but I like how they add a little something different to the cake design.
• Lastly, fill the cake in with drop flowers. You won’t have enough buttercream to pipe flowers on the sides of the cake, only on top.

• For other floral cake decorating ideas, see my carrot cake sheet cake with piped buttercream flowers.
• And as an alternative to the piping, simply dollop the buttercream onto the cake, and use an offset icing spatula to swirl and blend the colors together.

Recipe Variations

• 9×13 Inch Sheet Cake. For a larger sheet cake, double the cake recipe and bake it in a 9×13 inch baking pan. Increase the buttercream by 1 1/2 times.
• Layer Cake. Bake the cake batter in two or three 6-inch cake pans, or double the cake recipe and bake the cake batter in two or three 8-inch cake pans. I have not tested the bake times for these variations, so test the cake for doneness.

Be sure to read all of my BAKING FAQs where I discuss ingredients, substitutions and common questions with cake making, so that you can be successful in your own baking! I also suggest reading these comprehensive posts on making Perfect American Buttercream, How to Stack, Fill, Crumb Coat and Frost Layer Cakes and How to Use Piping Bags.

Frequently Asked Questions

Does this cake need to be refrigerated?

With blueberries baked into the cake batter, this cake can spoil more quickly if it’s not refrigerated. You can keep the cake stored in an airtight container at room temperature for up to 1 day, or in the refrigerator for up to 3 days. Let come to room temperature for several hours before serving.

Is this blueberry sheet cake supposed to be dense?

Yes, this is a more dense cake, somewhat like a pound cake. In order for the blueberries to stay suspended in the cake and not sink to the bottom, you need a thicker cake batter and a more dense cake.

Where can I find freeze dried blueberry powder?

I buy freeze dried blueberry powder on Amazon. I’ve used it mainly in buttercream, for a natural, vivid color and a punch of blueberry flavor.

What can I use instead of the blueberry powder?

You can use blueberry jam instead, but you’ll need to use a few tablespoons, and it can thin out your buttercream more than the powder. If you don’t want lumps of blueberries in your buttercream, you’ll need to pulse the jam in a small food processor first, for a smooth texture.

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