Heat a small, dry skillet over high heat and add the cumin seeds. Toast the seeds until fragrant, swirling the seeds occasionally so they toast evenly, 30 to 45 seconds. Transfer the seeds to a mortar and pestle or a spice grinder and grind to a coarse powder.
In a blender, combine the yogurt, water, tarragon, and salt and blend until smooth. Taste and adjust seasoning if needed. Divide