Preheat your oven to 350°F (175°C) to ensure the cake bakes evenly.
Grease and flour a 9×13-inch baking dish. In a large bowl, mix the white cake mix, flour, and strawberry Jello powder. Add water, oil, eggs, vanilla extract, and strawberry puree. Mix until smooth.
Pour the batter into the baking dish. Bake for 35-40 minutes, or until a toothpick comes out clean. Cool completely.
In a large mixing bowl, beat the cream cheese and butter until smooth. Add strawberry puree, then slowly add powdered sugar until desired consistency. Chill until ready to use.
Spread the chilled strawberry cream cheese frosting evenly over the cooled cake.
Slice the cake and serve with optional garnishes, such as fresh strawberries, a sprinkle of Jello powder, or white chocolate shavings.
Notes
Chill the frosting slightly before spreading to make it easier to work with. For extra strawberry flavor, top with fresh strawberry slices.