Lean Lasagna

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 mushroom s

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