Combine all ingredients in a medium bowl; taste and season with additional salt and pepper as desired. Refrigerate and serve chilled.
*To mellow out the flavor of the onion, soak it for 15 minutes in cold water after dicing, then drain, pat dry, and proceed with the recipe. Or if you prefer, you can use scallions or chives.
Notes
Use this dip for crackers, celery sticks, cucumbers, carrot sticks, sliced bell peppers, pita chips, or anything else you love to dip!