Bea’s Blueberry Sheet Cake is a soft, lemony buttermilk cake packed with fresh blueberries and spread with a pale purple blueberry cream cheese frosting. It bakes in one 9×13-inch pan and cuts into 15 squares, so it is an easy cake for summer cookouts, birthdays, church suppers and potlucks.
How to make blueberry sheet cake: Cream butter and sugar, beat in eggs and vanilla, then add buttermilk, the dry ingredients, lemon zest and juice. Fold in flour-dusted blueberries, bake at 350°F for 40 to 45 minutes and cool completely. Frost with cream cheese frosting whipped with blueberry jam.
Why You’ll Love It
- One pan: no layers to level or stack, and it travels in its own pan.
- Bright flavor: lemon zest and juice make the berries taste fresher.
- Pretty frosting: blueberry jam turns the cream cheese frosting a soft purple.
- Feeds a crowd: 15 generous squares.
Ingredient Notes
Buttermilk: One cup at room temperature. It keeps the crumb tender and adds a gentle tang. Cold buttermilk can make the creamed butter seize, so let it sit out with the eggs.
Fresh blueberries: A heaping cup and a half, tossed with a tablespoon of flour before folding in. The flour coating helps them stay spread through the cake instead of sinking to the bottom. Fresh berries hold their shape better than frozen, which bleed color into the batter.
Lemons: The zest of three lemons plus a quarter cup of juice. It sounds like a lot, but the zest is what gives the cake its bright, fresh taste. I zest the lemons before juicing them; it is much harder the other way around.
Butter and eggs: Softened butter and room temperature eggs cream into a light, airy batter.
Blueberry jam: A quarter cup in the frosting gives it color and berry flavor. A jam with real fruit and not too much syrup works best, and it keeps the frosting from getting too soft.
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Ingredients
For the cake:
- 3 cups all-purpose flour
- 1 tbsp all-purpose flour, reserved for coating the blueberries
- 2 tsp baking powder
- 1 tsp baking soda
- 1/2 tsp salt
- 1 cup unsalted butter, softened
- 1 1/2 cups granulated sugar
- 4 large eggs, room temperature
- 2 tsp vanilla extract
- 1 cup buttermilk, room temperature
- 3 lemons, zested
- 1/4 cup fresh lemon juice (about 2 lemons)
- 1 1/2 heaping cups fresh blueberries
For the frosting:
- 3/4 cup unsalted butter, softened
- 6 oz cream cheese, softened
- 1/4 cup blueberry jam
- 3 cups powdered sugar
- 1 tsp vanilla extract
- Fresh blueberries, for garnish (optional)
How to Make Blueberry Sheet Cake
The cake
1. Prepare the pan. Preheat the oven to 350°F. Grease a 9×13-inch baking pan and line it with parchment paper if you like.
2. Mix the dry ingredients. In a medium bowl, whisk together 3 cups flour, the baking powder, baking soda and salt.
3. Cream. In a large mixing bowl, beat the softened butter and granulated sugar for 2–3 minutes, until light and fluffy.
4. Add the eggs. Add the eggs one at a time, beating well after each addition.
5. Add the vanilla. Mix in the vanilla extract.
6. Add the buttermilk. With the mixer on low, gradually add the buttermilk. The mixture may look slightly curdled; that is normal.
7. Add the flour. Add the dry ingredients in two additions and mix only until combined.
8. Add the lemon. Mix in the lemon zest and lemon juice.
9. Add the berries. Toss the blueberries with the reserved tablespoon of flour, then gently fold them into the batter.
10. Fill the pan. Spread the batter evenly in the prepared pan.
11. Bake. Bake for 40–45 minutes, until a toothpick inserted in the center comes out clean.
12. Cool. Let the cake cool completely before frosting.
The frosting
13. Whip the butter. Beat the softened butter for 5–8 minutes, until pale and fluffy.
14. Add the cream cheese. Add the softened cream cheese and beat until smooth.
15. Add the jam. Mix in the blueberry jam.
16. Add the sugar. Gradually add the powdered sugar on low speed, then add the vanilla extract.
17. Whip. Beat the frosting for another 2 minutes, until light and fluffy.
18. Frost. Spread the frosting over the cooled cake and garnish with fresh blueberries if you like.
How to Keep the Blueberries From Sinking
Toss the berries in flour. The light coating gives them something to grip in the batter, so they stay suspended instead of sliding to the bottom of the pan.
Fold them in gently and last. Stirring hard breaks the berries and streaks the batter purple, and it can deflate the batter so it cannot hold the fruit. A few turns with a spatula is enough.
Keep the batter thick. This batter is thick enough to support the fruit as long as the butter is creamed well and the flour is measured correctly. Spoon the flour into the cup and level it; too little flour makes a thin batter that the berries fall through.
Tips for Success
Why is my frosting runny?
The cake was still warm, or the cream cheese and butter were too soft. Frost only a completely cool cake, and chill the frosting for 15 minutes if it seems loose.
Why is the cake dense?
The butter and sugar were not creamed long enough, or the batter was overmixed after the flour went in. Cream until fluffy and mix the flour only until combined.
Can I use frozen blueberries?
Yes. Do not thaw them; toss them in flour straight from the freezer and fold them in at the last second. Expect some purple streaks, and bake a few minutes longer if needed.
Variations
- Lemon frosting: use lemon zest and a little lemon juice in place of the jam.
- Mixed berry: use half blueberries and half raspberries.
- Glaze: skip the frosting and pour a simple lemon glaze over the cooled cake.
Storage
Because the frosting contains cream cheese, keep the frosted cake covered in the refrigerator and do not leave it out for more than 2 hours. Follow USDA FSIS guidance and eat leftovers within 3 to 4 days. Let squares sit out for a few minutes before serving so the frosting softens.
What to Serve With It
Serve squares on their own or with a scoop of vanilla ice cream. For more blueberry bakes, try lemon blueberry cake, blueberry pound cake or Amish blueberry oatmeal. For more cakes that feed a crowd, there is Texas sheet cake, Southern peach crumb cake and 7 Up pound cake.
Frequently Asked Questions
What are common blueberry cake mistakes?
Skipping the flour coating so the berries sink, stirring them in too hard so the batter turns purple, and frosting the cake before it is completely cool.
How do I make a moist blueberry cake?
Use buttermilk, measure the flour by spooning it into the cup, and take the cake out as soon as a toothpick comes out clean.
Can I make it ahead?
Yes. Bake the cake a day ahead and keep it covered at room temperature, then frost it on the day. Once frosted, keep it in the refrigerator.
Can I bake it in a different pan?
Two round cake pans work for a layer cake; start checking them early, since thinner layers bake faster.
Final Notes
Coat the berries in flour and let the cake cool completely before frosting. If you have a question or make it, tell me how it turned out in the comments.
Bea’s Blueberry Sheet Cake
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Ingredients
- 3 cups all-purpose flour for the cake
- 1 tbsp all-purpose flour reserved for coating the blueberries
- 2 tsp baking powder
- 1 tsp baking soda
- 1/2 tsp salt
- 1 cup unsalted butter softened, for the cake
- 1 1/2 cups granulated sugar
- 4 large eggs room temperature
- 2 tsp vanilla extract for the cake
- 1 cup buttermilk room temperature
- 3 lemons zested
- 1/4 cup fresh lemon juice about 2 lemons
- 1 1/2 heaping cups fresh blueberries
- 3/4 cup unsalted butter softened, for the frosting
- 6 oz cream cheese softened
- 1/4 cup blueberry jam
- 3 cups powdered sugar
- 1 tsp vanilla extract for the frosting
- fresh blueberries optional, for garnish
Instructions
- Preheat the oven to 350°F. Grease a 9x13-inch baking pan and line it with parchment paper if desired.
- In a medium bowl, whisk together 3 cups flour, baking powder, baking soda, and salt.
- In a large mixing bowl, beat the softened butter and granulated sugar for 2–3 minutes, until light and fluffy.
- Add the eggs one at a time, beating well after each addition.
- Mix in the vanilla extract.
- With the mixer on low, gradually add the buttermilk. The mixture may appear slightly curdled.
- Add the dry ingredients in two additions and mix only until combined.
- Mix in the lemon zest and lemon juice.
- Toss the blueberries with the reserved tablespoon of flour, then gently fold them into the batter.
- Spread the batter evenly in the prepared pan.
- Bake for 40–45 minutes, until a toothpick inserted in the center comes out clean.
- Let the cake cool completely before frosting.
- For the frosting, beat the softened butter for 5–8 minutes, until pale and fluffy.
- Add the softened cream cheese and beat until smooth.
- Mix in the blueberry jam.
- Gradually add the powdered sugar on low speed, then add the vanilla extract.
- Beat the frosting for another 2 minutes, until light and fluffy.
- Spread the frosting over the cooled cake and garnish with fresh blueberries if desired.
Notes
Nutrition
Nutrition values are estimates based on the listed ingredients and serving count. Actual values vary with brands, cuts and portion sizes.
