Mix the Batter: In a large mixing bowl, combine 1 (15.25 oz) white cake mix, 1 (3 oz) package strawberry Jell-O, and 4 large eggs. Next, add 1 cup vegetable oil, 1/4 cup water, and half of the 1 (10 oz) package frozen strawberries, thawed. Mix together using a hand mixer on medium speed for about 2 minutes. Your batter should be smooth and slightly thick.
Bake the Cake: Preheat your oven to 350°F. Pour the batter into a greased 12x9 inch baking pan. Make sure to spread the batter evenly across the pan. Bake in the preheated oven for 30 minutes, or until the cake is golden brown and a toothpick inserted in the center comes out clean. Once baked, remove from the oven and allow to cool completely in the pan on a wire rack.
Prepare the Frosting: In a medium bowl, combine 1 (1 lb) powdered sugar and 1/3 cup softened butter using a hand mixer on low until it’s crumbly. Gradually add the remaining thawed strawberries and continue mixing until the frosting is smooth and creamy.
Frost the Cake: Once your cake is completely cooled, use a spatula to spread the strawberry frosting evenly over the top of the cake. Be generous, allowing the frosting to puddle in any small dips for added decadence.
Slice and Serve: Cut the cake into 12 even slices and serve, enjoying the delightful mix of textures and flavors!