<<Disclaimer: Verify this information before applying it to your situation.>>

If you can't or don't want to use buttermilk in a recipe, there is a
viable substitute---plain yogurt.  You can easily find it in various
forms--besides cow's milk, you can find goats'milk yogurt and non-dairy
yogurt.

Some of the yogurts are very thick.  Just thin with water to the proper
consistancy.  I have found that a six ounce contain mixed with 2 ounces
of water yields a good consistency.  I have used this in muffin and
cornbread recipes.  Never had a problem~
Ann