This vegan sour cream recipe is the closest homemade version to the real thing I have ever had. Both flavor and texture are so close to the dairy version!
Place all ingredients in a blender and blend until smooth
Put in an airtight container and let set in the fridge overnight.
To make a nut free version, you can try subbing silken tofu for the nuts! Do the same amount, so 1 1/2 cups plus 2 tablespoons.