Let’s bake this fabulous Strawberry Sheet Cake! It’s easier than it looks and perfect for sharing. First, prepare your pan and oven. Preheat the oven to 350°F (175°C). Line the bottom of a 15x10x1-inch baking sheet with parchment paper, then lightly coat the parchment and the sides of the pan with cooking spray.

Make the Cake Batter: In a large bowl, whisk together the dry white cake mix, the dry strawberry gelatin powder, 3 tablespoons sugar, and 3 tablespoons all-purpose flour. Break up any large clumps.

Add the 1 cup water, 1/2 cup canola oil, and 2 beaten room temperature eggs to the dry ingredients. Beat with an electric mixer on low speed for 30 seconds just to combine. Then, increase the speed to medium and beat for 2 minutes, scraping down the sides of the bowl as needed.

Gently fold the 1 cup of finely chopped fresh strawberries into the finished batter using a spatula.

Pour the batter into the prepared baking sheet, spreading it evenly to the edges with your spatula.

Bake and Cool: Bake in the preheated oven for 15 to 16 minutes. The cake is thin, so it bakes quickly! It’s done when a wooden toothpick inserted into the center comes out clean.

Place the pan on a wire rack and let the cake cool completely in the pan. Don’t rush this step – frosting a warm cake leads to a melted mess!

Make the Frosting: While the cake cools, prepare the frosting. Place the 1/2 cup fresh strawberries in a food processor or blender. Pulse or blend until they are completely smooth and pureed. Set aside.

In the large bowl of a stand mixer fitted with the paddle attachment (or using a large bowl and handheld mixer), beat the 1 cup softened butter and 1 cup room temperature mascarpone cheese together on medium speed until light and fluffy. This usually takes about 3-5 minutes. Scrape down the sides of the bowl.

Beat in the 1/4 teaspoon salt and the reserved strawberry puree until combined.

With the mixer on low speed, gradually add the 3 1/2 cups of confectioners’ sugar, about one cup at a time, beating well after each addition. Once all the sugar is incorporated, increase the speed to medium-high and beat until the frosting is light, fluffy, and smooth.

Frost the Cake: Once the cake is completely cool, spread the strawberry mascarpone frosting evenly over the top using an offset spatula or a knife.

Slice the cake into squares or rectangles to serve. Store leftover cake covered in the refrigerator due to the mascarpone and fresh fruit in the frosting.