Stir the tahini and lemon juice together until well blended. Add the rest of the ingredients except the cucumbers and stir to blend.
Allow the mixture to stand at room temperature for about 30 minutes. (If you put it in the refrigerator, it will thicken up). If it is too thick to pour, you can use it as a dip for the cucumbers OR you can thin it out with room temperature water (NOT cold) which is what I do.
Peel the cucumbers and slice them into rounds. Put them in a large bowl and pour the dressing over them. Toss to coat.