Low Fat Chocolate Marble cake

Been not baking and kids are complaining they want to eat
cake. We have just finished a Sara Lee Chocolate Swiss pound
cake and that's the kids' favourite. So I went searching for a
pound cake recipe but knowing that pound cake is loaded with
butter, i search for a low fat one.

This one caught my eye, Low Fat Chocolate Marble cake from
here (Thanks Mandy). After reading, it doesnt seem too
difficult. It has yogurt as one of the ingredients and I know I
do not really like using yogurt, just don't quite like the texture
of the end product, but I guess, low fat, so no choice.

Everything went on quite smoothly, but I really don't know
how to make the swirl inside the cake, so I just mix the two
types of batter and get the kids to swirl the pattern on top.

In goes the cake, and the recipe says 45 minutes... but before
the time is up, the cake cracked.  I have to continue baking
cos the inside is not cooked. I ended up with a hard and burnt
crust. Anyway, the cake is still edible and with the chocolate
inside, it is still considered tasty. However, I noticed a greenish
patch at the bottom of the cake (did you spot it?) and am
wondering did that patch resulted from cake sinking after
cooling, or was it uncooked batter (told you i am still a newbie),
so I did not offer alot to my kids and eat most of them all up
myself (luckily the recipe says low fat).

Here's how it looks.


did you see the greenish "belt" below the chocolate part?

刚吃完Sara Lee的pound cake,孩子又吵要吃蛋糕，所以想
做个pound cake,但 pound cake 用很多牛油，所以找了个
low fat的巧克力云石蛋糕。
一切还算顺利， 直到烘烤时，还没够钟，蛋糕顶就裂开，里
面还没熟，所以就继续烘， 结果就有点焦了。
这蛋糕还真蛮好吃，但发现蛋糕底部有点青青的，不知是否
不熟，所以没给孩子多吃，自己把它给解决了（还好是低脂的)。