Start by patting dry the lamb using paper towels. Season the meat on all sides with salt and pepper and lightly dust the lamb with flour, shaking off any excess.
In a large pot or dutch oven, heat the olive oil and sear the lamb on medium-high heat. Sear the lamb until it has a nice brown colour on the outside. This might take about 6 minutes. Once cooked put the lamb aside and drain from any excess fat.
In the remaining fat, cook the onion for a few minutes until translucent. Add the garlic and the anchovy fillets, and let cook until the latter melt. Add the tomato paste and let it cook for about 3 minutes. Once the base is ready, add the seared lamb back to the pot.
Add the tomato passata, cumin, nutmeg, oregano, rosemary, chili flakes and bay leaves. Cover the pot and simmer on low heat for about 2 hours, stirring it occasionally so that the meat doesn't get stuck to the bottom. * Season again to taste with salt and pepper.
In the meantime, bring to boil a pot filled with water. Once it starts to boil, season with plenty of salt. Add the pasta and cook as instructed on the package or until al dente.
Once the pasta cooks add it to the ragù and serve with some grated parmesan cheese.
Notes
*If needed and it starts to dry out add some warm water.