Begin by gathering and measuring out all your ingredients. Chop the onion, dill, and capers finely, ensuring that they are ready to be mixed into the mayonnaise.
In a medium mixing bowl, add 1 cup of mayonnaise. This will serve as the creamy base of your tartar sauce.
Next, stir in 2/3 cup of sweet and/or dill pickle relish. Make sure to drain it lightly so that your sauce doesn’t become too watery. The relish adds that signature tang and sweetness.
Now, add 1 tablespoon of grated onion, 1 tablespoon of chopped capers, and 1 teaspoon of Dijon mustard. These ingredients will bring an extra layer of flavor that makes this tartar sauce special.
Sprinkle in 1/2 to 1 tablespoon of chopped fresh dill, and squeeze in 1 to 3 teaspoons of freshly squeezed lemon juice. If you prefer a touch of sweetness, add 1/2 to 1 teaspoon of granulated sugar at this point. Finally, season with kosher salt and freshly ground black pepper to taste.
Using a whisk or a spoon, mix all the ingredients together thoroughly. Taste your tartar sauce and adjust any components as necessary.
Transfer your homemade tartar sauce to a storage container and refrigerate for at least 30 minutes before serving. This allows the flavors to meld together beautifully.