There are several Spinach Lasagna recipes in the TKL archives, here is one of them:

Title: Family Pleasin' Spinach Lasagna
Posted By: Stephanie
Date: February 15th 1999
In Reply to: ISO: lasagne help needed!
Board: Vegetarian Recipe Swap

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1 tsp olive oil
1 large onion, chopped
1-28 oz can whole, peeled tomatoes, chopped
1 1/2 tsp oregano
1/2 tsp salt
1/2 tsp garlic powder
1/8 tsp pepper
9 lasagna noodles, uncooked
1-10 oz pkg frozen spinach, chopped and thawed, not drained
8 oz mozzarella cheese, shredded (use soy cheese, if vegan)

ADDITIONS FOR MORE PROTEIN: crumbled tempeh (very good); frozen, then thawed
and pressed tofu, crumbled; TVP crumbles, and of course, my favorite addition,
when I can afford them, portabella mushrooms, sliced. MMMMMMMMM.

In medium pot, heat oil over medium-high heat. Add onion, cook, stirring,
until tender; 8-10 minutes. Add tomatoes, oregano, salt, garlic powder,
pepper, and 1 cup water; bring to a boil. Reduce heat to low and simmer,
uncovered, 30 minutes. Preheat oven to 350 degrees. In bottowm of 13x9 pan
spread 1 cup sauce. Arrange 3 noodles on top of sauce. Lay 1/3 of spinach on
top of noodles. Lay 1/3 of tempeh or other addition on top of spinach.
Sprinkle 1/3 of the cheese on top of spinach. Repeat twice. Pour any
remaining sauce over top. Cover with foil and bake 45 minutes. Remove foil;
bake uncovered, 15 minutes. Remove from oven; let stand for 15 minutes to
set. Serve. Makes 8 servings.