Whisk tahini, garlic paste, lemon juice, olive oil, and salt in a bowl until combined. The mixture may thicken and look lumpy.
Whisk in the water, a tablespoon at a time, until you have your desired consistency. If making a spread, look for the consistency of peanut butter. For a sauce, add enough water to resemble the consistency of runny yogurt.
Stir in the optional cumin, cayenne pepper, and parsley.
Taste for seasoning and adjust with additional salt or lemon juice.
