Beat the cake mix and next 7 ingredients at low speed with an electric mixer 1 minute. Scrape down the sides, and beat at medium speed 2 more minutes, stopping to scrape down sides, if needed. (Strawberries should be well blended into batter.)
Pour batter into 3 greased and floured 9-inch cake pans.
Bake at 350° for 23 minutes or until cakes spring back when lightly pressed with a finger.
Cool in pans on wire racks for 10 minutes. Remove from pans; cool completely on wire racks.
Spread Strawberry Buttercream Frosting between layers and on top and sides of cake. Garnish, if desired. Serve immediately, or chill up to 1 week.
Note: I used Duncan Hines Moist Deluxe Classic White Cake Mix without pudding.
To make ahead: Place finished cake in the refrigerator, uncovered, and chill for 20 minutes or until the frosting sets. Cover well with wax paper, and store in the refrigerator for up to 1 week. To freeze, wrap chilled cake with aluminum foil, and freeze up to 6 months. Thaw overnight in the refrigerator.