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
Tbsp. oil in a large bowl to coat; season with
salt and pepper. Cover and chill 15 minutes.
Whisk yogurt and 1 Tbsp. water in a small bowl;
season with salt and pepper.
Heat remaining 2 Tbsp. 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 ½ 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.