crème fraiche is 1st choice , you can make buttermilk
with lemon and whole milk: They're using 2% here...
Ingredients
1 tablespoon white vinegar or lemon juice
1 cup 2% milk
Step 1: Stir together vinegar/lemon juice and milk
Add the white vinegar or lemon juice to a liquid measuring cup. Pour enough milk on top to measure 1 cup. Give everything a quick stir.
Step 2: Let it stand until curdled slightly
Let the mixture stand at room temperature for five minutes. Once the timer is up, your homemade buttermilk is ready to use!
Buttermilk Substitutes
Yogurt: Yogurt makes a great substitute for buttermilk. Just use 1 cup of yogurt for each 1 cup of buttermilk in your recipe. If using thick yogurt, like Greek or Icelandic yogurt, thin it with some water first before measuring out a cup.
Cream of tartar: If you dont have any vinegar in the house, break out your cream of tartar! Add 1-1/2 teaspoons of cream of tartar to 1 cup of milk, stir to combine and let the milk sit for five minutes before using it.
Sour cream: Sour cream is an excellent buttermilk substitute. To replace 1 cup of buttermilk, stir together 3/4 cup of sour cream with 1/4 cup of water.
Powdered buttermilk: You can also use powdered buttermilk, such as Saco Cultured Buttermilk Blend, which you can find on Amazon or near the dry and canned milk in the grocery store.
Is there a dairy-free buttermilk option?
You bet. To make dairy-free buttermilk, combine 3/4 cup of plain or vanilla almond milk yogurt with 1/4 cup of almond milk and 1/2 teaspoon of white vinegar. Let it stand for 5 to 10 minutes before using it.
https://www.tasteofhome.com/recipes/how-to-make-buttermilk-recipe/
HTH!