In a medium bowl, whisk together ¼ cup tahini, ¼ cup plain Greek yogurt, 2 Tbsp lemon juice, 2 tsp capers, 2 tsp caper juice, 1 tsp Dijon mustard, 3 cloves garlic (minced), ¼ tsp each salt and pepper, and 2 Tbsp cold water (may need more depending on how thin you want the sauce)