Preheat oven to 350 degrees. Spray 9x13 cake pan with baking spray or grease with butter.
Mix all of the cake ingredients together, scrape the bowl at least once. Pour batter in pan and bake for 25 minutes or until toothpick comes out clean when poked into cake.
frosting
Whip butter with mixer, gradually add in 1/2 of the powdered sugar, add vanilla continue to mix add in a couple of tablespoons of mashed strawberries, continue to add the remaining sugar, alternating with tablespoons of mashed strawberries until the consistency is what you like.The frosting can be a bit looser if you are making a sheet cake, it will need to be stiffer if you are making a layer cake.