LEMON BLUEBERRY MARBLE CAKE: White Cake made w/Lemon Extract & Blueberry Jam swirled Into batter! Then Blueberry Jam between cake layers & frosted with Lemon Buttercream Frosting! VERDICT: This was Lovely! Just used White Cake Mix, swirled w/Blueberry Jam mixed w/Lemon Juice. White Frosting mixed w/Blueberry Jam and Lemon Juice. Can't Imagine how good it will be when I follow true recipe!