Heat oven to 425. Spray an 8" square baking dish w/ cooking spray. In lg bowl, combine ricotta cheese, mozzarella cheese, nutmeg, 1/4 cup parmesan cheese and salt & pepper to taste. Fold in spinach
Spread 1/2 cup of squah into bottom of baking dish. Top w/ 2 lasagna noodles. Spread 1/4 cup of the remaining squash over noodles. Dollop w/ 1 cup ricaotta mix. Repeat. Place the last 2 noodles on top, spread w/ reamining squash and dollop w/ remaining ricotta mix.
Sprinkle w/ remaining parmesan cheese. Spray a lg piece of foil w/ cooking spray and place on top of casserole. Bake 15 mins. Uncover and bake 10 more mins, or until noodles are tender and top is golden brown.