Prepare the strawberries by thawing and pureeing them in a blender or food processor until smooth. Reserve some for the frosting.

In a large mixing bowl, combine the white cake mix and strawberry-flavored gelatin. Whisk until well blended.

In another bowl, beat the softened butter and cream cheese together until light and fluffy, about 2-3 minutes.

Add the pureed strawberries, eggs, vegetable oil, and water to the dry mixture. Beat on medium speed for 1-2 minutes until smooth.

Pour the batter evenly into prepared cake pans and bake in a preheated oven at 350°F (175°C) for about 20 minutes. Check for doneness with a toothpick.

While the cakes cool, prepare the frosting by adding the remaining pureed strawberries and strawberry extract to the creamed butter and sugar. Gradually mix in the powdered sugar until smooth.

Once the cakes are completely cool, place one layer on a serving plate and spread one-third of the frosting on top. Add the second layer and frost the top and sides with the remaining frosting.

Garnish with fresh strawberry slices and chill in the refrigerator before serving.