Add the lemon juice and the unpeeled garlic cloves to a blender. Pulse them about 15 times until all the garlic gets crashed. Let them infuse for 15 mins.
Strain the mixture to remove all the skins and the bigger pieces of garlic (press with a spoon to get all the juices out), and mix the strained liquid with one cup of tahini.
Start adding cold water one tablespoon at a time and continue to mix until you get a soft, creamy texture.
Add salt to taste and one teaspoon of cumin. Store in the fridge in an air-tight glass jar. It will last for at least one week.