In a food processor or high speed blender, add the tahini and about half cup water. Pulse a couple of times to incorporate the ingredients.
Add the lemon juice, garlic, cumin, salt and pepper and pulse a few times until you have a smooth creamy paste.
Add water gradually and pulse after each addition, until you get the desired consistency. The amount of one cup of water to one cup pf tahini gives a hummus like texture to the sauce. If you would like to have a thinner sauce (e.g. to drizzle over grilled meats or a salad) then you need to add more water.