Why do you have to use cream of tartar in meringue?
Composition. Tartar sauce is based on either mayonnaise (egg yolk, mustard or vinegar, oil) or aioli (egg yolk, olive oil, garlic, lemon juice), with certain other ingredients added. In many places, cream of tartar is used. In the UK, recipes typically add to the base capers, gherkins, lemon juice, and dill.