This Peanut Butter Sheet Cake is a dreamy, crowd-pleasing dessert that combines rich, nutty flavors with a melt-in-your-mouth texture. The moist, tender cake is perfectly balanced by a creamy peanut butter frosting that’s both indulgent and comforting. In just under an hour, you can create a treat that’s as easy to make as it is irresistible, ideal for gatherings or a sweet weeknight surprise.
Every bite offers a delightful contrast of soft cake and velvety frosting, with a hint of sweetness that’s never overwhelming. The warm aroma of peanut butter fills your kitchen as it bakes, promising a dessert that’s as satisfying to smell as it is to taste. Whether you’re a peanut butter lover or just seeking a dessert that feels like a hug, this cake delivers in every way.
Ingredients for Peanut Butter Sheet Cake
- Sheet Cake:
- 2 cups (250 g) all-purpose flour
- 1 cup (200 g) granulated sugar
- ¾ cup (150 g) light brown sugar (firmly packed)
- ¾ teaspoon baking soda
- ¾ teaspoon salt
- 1 cup (237 ml) water
- ¾ cup (177 g) unsalted butter (cut into pieces)
- ¼ cup (60 g) canola or vegetable oil
- ½ cup (145 g) creamy peanut butter
- ½ cup (118 ml) buttermilk (or substitute with milk + ½ tsp vinegar)
- 2 large eggs (room temperature preferred)
- 1 ½ teaspoons vanilla extract
- Fudgy Peanut Butter Frosting:
- 4 cups (500 g) powdered sugar (sift if lumpy)
- ½ cup (118 ml) buttermilk (or substitute with milk + ½ tsp vinegar)
- 10 Tablespoons (150 g) unsalted butter (cut into pieces)
- ⅔ cup (165 g) creamy peanut butter
- ¼ heaping teaspoon salt
- 1 teaspoon vanilla extract
Step-by-Step Instructions
- Preheat oven to 350°F (175°C) and lightly grease a 13×9 baking pan. Set aside.
- In a large bowl, whisk together flour, granulated sugar, brown sugar, baking soda, and salt.
- In a medium saucepan, combine water, butter, and oil. Heat over medium heat, stirring occasionally, until butter melts and the mixture comes to a boil.
- Once boiling, remove from heat and add peanut butter. Stir until smooth and fully dissolved. Pour this mixture into the bowl with dry ingredients and stir until combined. Let cool for 5-10 minutes.
- In a separate bowl, whisk together buttermilk, eggs, and vanilla extract.
- Gradually stir the buttermilk mixture into the batter until just combined.
- Pour the batter evenly into the prepared pan and bake on the center rack for 30-32 minutes, or until a toothpick inserted in the center comes out clean or with moist crumbs.
- Prepare the frosting: Measure powdered sugar and set aside (sift if needed).
- In a medium saucepan, combine buttermilk, butter, peanut butter, and salt. Cook over medium-low heat until butter melts, then increase heat to medium and bring to a boil, stirring constantly. Remove from heat immediately.
- Add powdered sugar and vanilla extract to the saucepan. Whisk until smooth.
- Immediately pour the frosting evenly over the warm cake (still in the pan). Let cool before serving.
Delicious Topping and Serving Ideas
Enhance your Peanut Butter Sheet Cake with a drizzle of warm caramel sauce or a sprinkle of chopped peanuts for extra crunch. For a fun twist, serve with a scoop of vanilla ice cream or a dollop of whipped cream. These additions can turn your cake into a show-stopping dessert for any occasion.
Storage and Reheating Tips
Store your cake in an airtight container at room temperature for up to 2 days or in the refrigerator for up to 5 days. To keep it fresh, cover it with plastic wrap or aluminum foil. If you prefer it warm, reheat individual slices in the microwave for about 10-15 seconds before serving.
Time-Saving Tips for Busy Bakers
To save time, measure all your ingredients before you start baking—this is called mise en place. Use a kitchen scale for accurate measurements to avoid multiple spoon or cup cleanups. Additionally, prepare your frosting while the cake is baking to make the process more efficient.
Equipment Guidance for Perfect Results
Ensure you have a 13×9 baking pan that’s well-greased to prevent sticking. An electric whisk or stand mixer can make combining the ingredients quicker and easier. For precise baking, use an oven thermometer to confirm the temperature is accurate, as oven settings can vary.
Common Questions Answered
Can I use natural peanut butter?
Yes, but the texture might differ slightly.
Can I substitute buttermilk?
Mix ½ cup milk with ½ tablespoon lemon juice or vinegar as a quick alternative.
How do I know the cake is done?
Insert a toothpick; if it comes out clean or with moist crumbs, the cake is ready
Peanut Butter Sheet Cake
Ingredients
Sheet Cake
- 2 cups all-purpose flour 250 g
- 1 cup granulated sugar 200 g
- ¾ cups light brown sugar 150 g, firmly packed
- ¾ teaspoon baking soda
- ¾ teaspoon salt
- 1 cup water 237 ml
- ¾ cup unsalted butter 177 g, cut into pieces
- ¼ cup canola or vegetable oil 60 g
- ½ cup creamy peanut butter 145 g
- ½ cup buttermilk 118 ml
- 2 large eggs room temperature preferred
- 1 ½ teaspoons vanilla extract
Fudgy Peanut Butter Frosting
- 4 cups powdered sugar 500 g
- ½ cup buttermilk 118 ml
- 10 Tablespoons unsalted butter 150 g, cut into pieces
- ⅔ cup creamy peanut butter 165 g
- ¼ heaping teaspoon salt
- 1 teaspoon vanilla extract
Instructions
- Preheat oven to 350F (175C) and lightly grease a 13×9 baking pan. Set aside.
- In a large bowl, whisk together flour, sugars, baking soda, and salt.
- In a medium-sized saucepan, combine water, butter, and oil. Heat over medium heat, stirring occasionally until butter is melted and bring to a boil.
- Once boiling, remove from heat and add peanut butter. Stir until peanut butter is dissolved and mixture is smooth. Add to bowl with dry ingredients and stir until combined. Set aside to cool for 5-10 minutes.
- Meanwhile, in a separate bowl, whisk together buttermilk, eggs, and vanilla extract.
- Gradually stir buttermilk mixture into batter, stirring until just combined.
- Pour batter evenly into prepared pan and transfer to center rack of 350F (175C) preheated oven and bake for 30-32 minutes or until a toothpick inserted in the center comes out clean or with moist crumbs. Prepare frosting.
- Fudgy Peanut Butter Frosting: Measure out sugar and set aside (if you’re worried about lumps in your icing, sift the sugar after measuring).
- Combine buttermilk, butter, peanut butter, and salt in a medium-sized saucepan. Cook over medium-low heat until butter is melted. Increase heat to medium and bring to a boil while stirring constantly. Once boiling, remove from heat.
- Immediately add powdered sugar and vanilla extract.
- Whisk until smooth and immediately pour evenly over cake (in the pan, I do not remove my cake from the pan).