Schwarma (many different spellings) is the Arab word to the Greek equivalent Gyros.
Traditionally, schwarma is accompanied by Tahini sauce and Gyros is accompanied by Tsaziki (many spellings) sauce.
Tahini Sauce is traditionally tahini (toasted or untoasted sesame butter), mixed with garlic, olive oil, lemon juice, and water to get the consistency you want. Sometime a bit of paprika, or cayenne or cumin is added. Sometimes some chopped flat leaf parsley is also added.
Tzasiki Sauce is traditionally a yogurt based sauce with cucumber, garlic, lemon juice.
Ocassionally, you will find Middle Eastern versions of tahini sauce adding yogurt or yogurt cheese because it "stretches" the sauce and is cheaper than using all Tahini.
Yogurt cheese is simply Plain (not vanilla) yogurt hung in a cheesecloth overnight until is congeals into a thicker cheese like consistency.
I prefer toasted sesame tahini, with no yogurt, lemon juice, fresh garlic, a little olive oil, some cayenne and some water, all processed, adding a bit of water until I get a fairly thick sauce but not one that I could stand a spoon up in!
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