I didn't taste the dressing you are talking about....but likely inclusions would be salt, black pepper, lemon juice or vinegar and very often MSG.
Linda C

This place prides itself on not using MSG. If they did, I'd have an allergic reaction (main reason I have to make my own in the fist place), so I am fairly sure they are telling the truth that they don't use it. Black pepper might be in it, but it is not "sharp" enough to have vinegar or lemon juice. The tang tastes like it is just from the sour cream. I'll start with this, maybe some paprika, and go from there.

Thanks for suggesting the black pepper!

I also am allergic to MSG....but I find I get a better Ranch dressing using butter milk and mayo....like the original recipe, than sour cream
Butter milk and mayo....about 2/3 buttermilk.
Garlic salt, parsley, black pepper....and a biut of something sour....a dash of rice wine vinegar, and a scosh of cayenne or tobasco...not much!
Linda C

I wonder if I could use buttermilk with sour cream. Aha! Cayenne instead of paprika! Much better idea. :-) One way or another I'll figure something out, and it helps to have suggestions. Thanks!!!