How do you make buttermilk out of skimmed milk?

To make buttermilk from skimmed milk, simply add an acidic ingredient. Mix one tablespoon of white vinegar or lemon juice into one cup of skimmed milk and let it sit for about 5-10 minutes until it thickens slightly and curdles. This creates a tangy flavor and texture similar to traditional buttermilk, making it suitable for baking or cooking.