Homemade Ranch dressing beats store-bought any day. Use the best quality ingredients you can find. Brands differ in taste, and all are not created equal.
1 cup mayonnaise
1/2 cup buttermilk (or more to thin)
1 Tablespoon parsley flakes
1/2 teaspoon onion powder
1/4 teaspoon garlic powder
1/4 teaspoon white pepper
1/8 teaspoon salt
My extra additions:
1/2 teaspoon minced dried onion
1/4 teaspoon dried dill weed
Combine all ingredients, stirring well.
Cover and chill dressing at least 4 hours.
Adapted from The Southern Living Cookbook, 1987