Lean Lasagna

Name: Lean Lasagna
Ingredients: Vegetable-oil cooking spray; 1/2 cup chopped onion; 1 lb ground turkey breast; 3 cups tomato sauce; 3 tsp Italian seasoning (or 1 tsp each dried basil, parsley, and oregano); 1/4 tsp freshly ground black pepper; 1/4 tsp garlic powder; 1/2 cup chopped mushrooms; 6 cups chopped fresh spinach (or chard); 2 cups fat-free ricotta; 1/4 tsp nutmeg; 1 package whole-wheat lasagna noodles(about 8 oz, or 9 noodles); 2 cups (8 oz) shredded part-skim mozzarella