In a medium bowl, stir together mayonnaise, relish, onion, capers, Dijon mustard, and ½ tablespoon fresh dill.
Season to taste with lemon juice, sugar (optional), additional dill (if needed), salt (only if needed), and pepper.
Cover the Tartar Sauce and refrigerate it for at least an hour, preferably 2-4 hours, or overnight for the flavors to meld. (It tastes better with time!)
Store in the refrigerator, tightly covered, for 5-7 days. Serve with your favorite seafood dishes or veggies. (See the "Serving" section in the article above for suggestions.)
