Heat a large skillet over high. Add a few drops of water and they should sizzle when the pan is ready. Or heat a drizzle of oil instead. Add cumin seeds and red chili pepper. Toast them for 1 to 2 minutes, until fragrant.
Transfer the yogurt and tahini to a medium bowl. Add the toasted seeds with red chili peppers.
Add lemon zest and juice. Mix well to combine, adding water until the desired consistency. Garnish with cilantro.