prepare the onions
In the same skillet, cook the lamb over moderately high heat, breaking it up, until no pink remains, 3 minutes. Pour off all but 1 tablespoon of the fat and add the ancho chile powder and cinnamon. Cook over moderately high heat, stirring, for 1 minute. Stir in the spinach. Transfer the lamb filling to a large bowl. Stir in the bread crumbs, Gruyère, 1/4 cup of the beef broth and 1/2 cup of the crushed tomatoes.