Preheat the oven to 300F.
In a large, heavy skillet, braising dish or ovenproof Dutch oven, heat a drizzle of oil over medium-high heat and brown the lamb in batches, getting it nice and dark on all sides and sprinkling with salt as it cooks. Transfer the meat to a plate as it browns so that you don’t crowd the pan. Add the onion and garlic to the pan and cook for a few minutes, until golden. Return the meat to the pan along with the spices and cook for a minute, then sprinkle the flour overtop and stir to coat the meat.
Add the lentils (if you’re using them), tomatoes and a can full of water, stirring to loosen any browned bits from the bottom of the pan. Grate in some of the lemon zest, then cut the lemon in half, squeeze the juice into the stew and toss in the lemon halves as well. Add the cinnamon stick, pomegranate molasses and honey.
Stir, cover and transfer to the oven for 2-2 1/2 hours, stirring once or twice if you think of it, making sure the liquid hasn’t cooked down too much. (If it seems dry, add more water.) The stew can be made ahead, cooled and refrigerated for a few days — just rewarm it when you’re ready to bake.
Increase the oven temperature to 375F. Leave the mixture in the baking pan or pot, or transfer it to a pie plate or shallow baking dish. Brush each sheet of phyllo with melted butter and crumple it up like a piece of newspaper, arranging the pieces on top of the stew. Bake for about 30 minutes, until the pastry is deep golden and the stew is bubbling around the edge. The original recipe suggested topping with sliced almonds and pomegranate arils, but I find it beautiful as is.