Lamb Stir-Fry with Pomegranate and Yogurt

Toast cumin and coriander seeds in a small dry skillet over medium heat until fragrant, about 1 minute. Let cool, then finely chop. Toss lamb with cumin, coriander, paprika, garlic, vinegar, and 2 tablespoons oil in a large bowl to coat; season with salt and pepper. Cover and chill 15 minutes. Whisk yogurt and 1 tablespoon water in a small bowl; season with salt and pepper. Heat remaining 2 tablespoons oil in a large skillet, preferably cast iron, over medium-high heat. Working in batches, cook lamb, tossing occasionally, until browned, about 5 minutes per batch; transfer to a plate with a slotted spoon. Add onion to skillet and cook, stirring often, until beginning to brown and soften, about 3 minutes. Add 1/2 cup water; season with salt and pepper and cook, stirring occasionally, until onion is tender and water is evaporated, about 3 minutes. Return lamb to skillet and toss to combine. Season with salt and pepper. Serve lamb over rice, topped with yogurt, pomegranate seeds, pistachios, and herbs. DO AHEAD: Lamb can be marinated 1 day ahead. Keep chilled.