I use a cake mix extender recipe and have been asked not to use sour cream ..no diary. Is there a suitable substitution for it or should I just omit it and how will omitting it change the constitency/density of the cake?

. . . equal parts apple sauce for sour cream is one alternative . . . but you may want to do a test run to ensure you are happy with the results in your recipe . . .

Here's my disclaimer: I haven't tried this, so if it doesn't turn out, it's not my fault. BUT, if you do an internet search for "Chocolate Mayo Cake," you'll find a bunch of recipes. I know that mayo will add a lot of moisture, so in that area, it can be a sub for the sour cream, but it is an egg product, so you may have to omit an egg or two. The recipes you'll find are from scratch, but it might work as an extender, as well. If you've got some trial and error time, it might be worth a shot. Please don't shoot me if this is the grossest thing ever.

LOL, I was going to chime in and say yogurt...but DUH. Yogurt is dairy too.

"tofutti" has recently come out with a non-dairy sour cream. I used it in a cake recipe last week and it was delish - you could not tell the difference!!