1 pound sweet Italian sausage (casings removed)
32 ounces ricotta cheese (4 cups)
2 large eggs
2 packages (10 ounces each) frozen chopped spinach, thawed
6 cups marinara sauce
12 no-boil lasagna noodles (8 ounces)
4 cups shredded fontina cheese
Spread a thin layer of tomato sauce on the bottom of a 9-by-13-inch glass baking dish. Arrange a layer of noodles on top. Spread one-third of the ricotta mixture over noodles, followed by one-third of the marinara sauce, then one-third of the sausage; sprinkle with one-third of the fontina cheese. Repeat to make two more layers, ending with cheese. Cover with aluminum foil; bake 30 minutes. Remove foil; continue baking until golden brown on top and sauce is bubbling, about 15 minutes more. Let cool slightly before slicing into squares and serving.