In a medium jar or bowl, whisk together ¼ cup milk and 1 tablespoon fresh lemon juice until well incorporated, then let it sit for 5 minutes. This is essentially homemade buttermilk.
To the homemade buttermilk mixture, add ¼ cup plain Greek yogurt (or mayonnaise), ¼ cup sour cream, ½ teaspoon dried dill weed, ½ teaspoon dried parsley, ¼ teaspoon onion powder, ¼ teaspoon garlic powder, ⅛ teaspoon dried basil, ¼ teaspoon kosher salt, and a pinch finely cracked pepper, and whisk until well combined.
Place the dressing in an airtight container and refrigerate for at least 30 minutes before using, to allow the flavors time to develop.
After 30 minutes serve as desired or store in the refrigerator for up to 7 days. Shake before each use.
Notes
In place of the dried spices, feel free to use 2 teaspoons of dried Ranch Seasoning. Milk + Lemon Juice: Feel free to replace the two with buttermilk. For milk, use any fat percentage of milk you have on hand.Yogurt: Using yogurt instead of mayonnaise will lower the fat in the dressing and make it egg-free. Be sure to use PLAIN Greek yogurt, not flavored yogurt or regular plain yogurt. Sour Cream: Use regular or reduced-fat, not fat-free sour cream for best results.