Spinach Tofu Lasagna

1 chopped onion
6 to 8 sliced mushrooms
1 bunch spinach or 1 (10 ounce) package frozen spinach, thawed
1 (16 ounce) container firm tofu, drained and crumbled
1 (32 ounce) jar pasta sauce
2 cups shredded Cheddar cheese
1 package lasagna noodles, cooked and drained
2 tablespoons vegetable seasoning

Preheat oven to 350 degrees F.

In nonstick skillet, saut