ibeeflower and hbquikcomjamesl, I don't have electronic versions of very many of my recipes yet but basically it's this:
I make a regular butter cake and replace the vanilla with lemon extract, replace a couple of tablespoons of the liquid with lemon juice and add some lemon zest. Before adding the lemon flavors, I take about 1 1/2 cups of the batter for the raspberry swirl and add some pureed and deseeded raspberries, a little raspberry flavoring and a tiny bit of pink food color. It works with a scratch recipe or a cake mix.
My raspberry buttercream is just my regular ABC with the liquid replaced with pureed, deseeded raspberries, raspberry flavor, and a tiny bit of pink food color.
It looks really pretty when it's cut, especially when torted because the frosting matches the swirl in the cake.
Thank you for this Elcee. Like I said, I've never made a marble cake. I am making the vanilla/chocolate combination. If you had to guess, is there a ratio I should be aiming for?
I wasn't sure if a marble cake was 50/50 (50 lemon/50 raspberry in your case).