High Altitude Lemon Blueberry Sheet Cake

A moist and dense lemon blueberry cake, frosted with lemon and blueberry cream cheese buttercream in pretty piped florals.

All recipes on Curly Girl Kitchen are developed for high altitude at 5,280 feet. See FAQs for adjusting to higher or lower elevations.

5 from 1 vote

Prep Time 30

Cook Time 40

Total Time 1 10

Course Dessert

Cuisine American

Servings9

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.

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.

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.

This cake should be stored in an airtight container at room temperature for up to 1 day, or in the refrigerator for up to 3 days.

Keyword Blueberry, Buttercream Flowers, Cake Decorating, Floral, High Altitude, Lemon, Sheet Cake