I make this every year for Jason's birthday.
This year (2023), I've changed how to marble the cake to make it more marbled. Instead of putting batter into the pan in globs, I decided it might be better to put it in layers.
This recipe does not use baking powder - mainly because I don't like the taste of baking powder. The light part of the cake rises because there is a base (baking soda) and an acid (orange juice) in it. (Baking powder is more or less a base plus an acid plus a filler.) The dark part of the cake rises because of the base (baking soda) and the acid (cocoa). Sugar is added to the cocoa mixture for sweetness, and milk is added to keep both batters at the same consistency.
Preheat oven to 350F. Grease and flour 9x13" pan.
In large bowl, cream
1/2 c butter
1 c sugar
1 t vanilla sugar (or vanilla extract)
1 t baking soda
1/2 t salt
Beat in
2 large eggs
Add, alternately,
2 c flour
1 c milk.
Batter should be on the thin side.
Place 1 c of batter in smaller bowl. Stir in:
1/4 c cocoa powder
2 T sugar
2 T milk
Add to leftover batter,
3 T orange juice.
Using
larger bowl, spread a thin layer of batter into pan. It doesn't need
to cover it entirely. Using entire smaller bowl, spread a layer of cocoa batter on
top. Then spread the rest of the larger bowl on top of that. Swirl together gently.
Bake 350F for 42 - 47 min.