How do I make 3/4 cup of buttermilk?

I would make 1 cup of buttermilk (see recipe below) and only use 3/4 cup of it.

Add 1 Tb. of white vinegar or lemon juice to a 1 cup measuring cup. Add milk to the 1 cup mark. Let it set for 5 minutes.

Milk Into Buttermilk

Mix 3/4 cup plain yoghurt with 1/4 cup milk or

In a cup place 1 tablespoon of lemon juice and top with milk. Let it stand for 2 minutes to turn.

In a cup mix a litttle milk with 3/4 teaspoon of cream of tartar. When smooth add the remaining milk to the top.

take 3/4 cup of soured milk, or 3/4 milk and some lemon juice. Or, next time you go to store, look for powered butter milk. Some stores (but unfortunatley not all stores) have it.

the easiest way is to combine almost 3/4 cups of milk with a tablespoon of vinegar! or, you can use lemon juice i guess.