Strain 2 cup greek yoghurt through a cheesecloth or coffee filter until it forms a very thick consistency, this will take approximately an hour.
In a pan on low heat, toast ¼ cup black sesame seeds for 1-2 minutes.
Put 10 cloves of garlic in ¼ cup olive oil in a non stick saucepan and heat on the lowest heat setting for 15-20 minutes. Remove from heat and let it cool.
In a food processor, grind the sesame seeds, oil and garlic mixture into a paste.
In a mixing bowl add the strained greek yoghurt, the sesame garlic paste and the zest of 1 lemon and juice of ½ lemon. Add salt and pepper to taste and mix well.
To serve, sprinkle over 1 tablespoon of sumac.
