Place the diced onion, minced garlic, cumin, coriander, paprika, cinnamon, and ginger into the slow cooker. Stir to combine.
Add the lamb cubes on top of the spice mixture. Drizzle with olive oil, then sprinkle with salt and pepper. Stir to coat the lamb evenly.
Pour the diced tomatoes with their juice and the beef broth over the lamb. Do not stir after adding the liquid.
Add the shredded cabbage on top. Cover and cook on low for 7 to 8 hours or on high for 4 hours until the lamb is tender.
Stir the cabbage into the lamb and sauce before serving. Sprinkle with chopped parsley.