Heat oven to 350 degrees F. Grease and flour two 8-inch round layer-cake pans. Puree berries.
Prepare cake mix as per package directions, substituting 1/2 cup reserved strawberry liquid for 1/2 cup of the water called for on package. Stir in food coloring and pureed berries. Divide in pans.
Bake in 350 degree F oven 30 minutes, until toothpick tests clean. Cool in pans on racks 10 minutes. Invert cakes; cool completely. Trim layers level. Stir jam into frosting; use to stack layers. Frost sides and top. Garnish with halved strawberries. Makes 12 servings.