In a large heavy dutch oven with a cover ( I used a Le Creuset pot), heat 3 tablespoons of olive oil over medium-high heat. When the oil is hot, brown the lamb - working in batches so the meat is not crowded. Adjust the heat as necessary to avoid burning the meat. When the lamb is browned on all sides about 10 minutes per batch, transfer to a platter with a tongs or large slotted spoon . Immediately season with salt and pepper. Repeat until all the lamb is browned, adding more olive oil as needed.
Leave the remaining fat in the pot and adjust the heat to medium. Add the sliced onions and a pinch of salt. Stir the onions around to coat with the oil and scrape the bottom of the pot to loosen any browned bits from the meat. Cook for about 15 minutes or until the onions take on a golden color.
Add the ginger and garlic and cook for 1 minute. Then add the cumin, coriander, turmeric, and Aleppo pepper flakes. Stir to combine. Add the lamb and any juices back to the pot, stir to combine. Add the yogurt, grated apple, and 1 cup of hot water, stir again to combine. The liquid should just cover the meat. Cover the pot and simmer gently for about 1½ hours or until the lamb is fork tender.
Serve the lamb curry with Basmati rice and a French bistro carrot salad. Optional, garnish with cilantro.