The sneaky trick here is using cashew sour cream instead of regular sour cream. (downshiftology.com)
You can use regular sour cream, but once baked into the cake, if anyone can tell the difference, I'd say that's one sharp palate they've got there. (davidlebovitz.com)
Of course, if you do eat dairy, feel free to use regular sour cream and / or cheese. (downshiftology.com)