Whisk lemon and garlic: Transfer the lemon juice to a medium bowl. Press the garlic into the bowl using a garlic press, or mince and add. Whisk to combine.
Add cumin, and salt. Whisk to combine.
Add the tahini and whisk the mixture until fully incorporated.
Add water: Add 2 tablespoons ice water at a time and whisk until smooth. The mixture may seize but it will eventually become creamy and smooth. Use up to 6 to 8 tablespoons water, or the amount needed for the desired texture.