In a large pot, sauté onion in oil until translucent.
Add the lamb, turmeric, and curry powder or garam masala and stir until the meat is no longer pink on the outside.
Add the tomatoes, carrots, salt, and any optional vegetables (except the spinach).
Simmer uncovered over low heat for 45 minutes.
Add peas (and spinach, if using), stir and cook briefly until heated through.
Serve over couscous or rice, or with naan or another Indian flatbread.