In Julia Child's Mastering the Art of French Cooking, Volume 1, which I got for my birthday this year, I learned that authentic Sauce Tartare is made with hard-cooked egg yolks, and Sauce Remoulade is made with raw egg yolks. That is, it is based on mayonnaise. Both have herbs, pickles, and capers, so except for the state of the egg yolks, they are virtually identical.
Well. I am from New England, and where I come from, Tartar Sauce is based on mayonnaise, mostly comes in a jar, and never saw a caper, so that's the way I like it. Now that I am allergic to soy, I can't buy it in a jar anymore, so I had to learn to make it myself. Here is the latest, and best so far (better than the stuff in the jar), version:
1/2 cup soy-free mayonnaise*
2 Tbsp sweet pickle relished, drained
1 Tbsp chopped fresh parsley (it is the fresh parsley that makes this so good)
2 tsp fresh lemon juice
1 tsp grainy mustard
1 1/2 tsp minced onion OR
1/2 tsp dried onion flakes
Don't use light mayo; the sauce will be runny. Combine all the ingredients in a small bowl and let set a few minutes to soften the onion flakes (if using) and let the flavors mix.
*Soy-free mayonnaise is a lot easier to find these days; you can even buy Hellman's Canola Mayonnaise (Best Foods west of the Rockies) at the grocery store now. For a long time I had to go to the health food store for Hain's Safflower Oil Mayonnaise, and that is still my favorite. Hain also has a Light Safflower Oil mayo that is pretty good, and we use that most of the time. Right before passover you can buy Kosher for Passover mayonnaise in the kosher section of the grocery store, too. (Many Jews avoid legumes during passover, and soybeans of course are legumes.)
Back to the tartar sauce. Like I said, being from New England, we ate a lot of fish, fried clams, and scallops growing up, most of the time involving tartar sauce. We even ate tartar sauce with our French fries, if it was available. When my brother tasted this version, his comment was something like, "Umph. Good tartar sauce," which is high praise indeed coming from a New England male.