Step 1

Preheat an oven to 375 degrees F (190 degrees C).

Step 2

Bring a large pot of lightly salted water to a boil. Cook lasagna noodles in boiling water for 8 to 10 minutes. Drain noodles, and rinse with cold water.

Step 3

Heat the olive oil in a skillet over medium heat. Stir in the onion; cook and stir until the onion has softened and turned translucent, about 2 minutes. Add ground turkey and cook 5 to 7 minutes more, stirring to break up any large chunks of meat. Stir in tomato sauce, mushrooms, Italian seasoning, black pepper, and garlic powder. Simmer for 2 minutes and season to taste.

Step 4

Combine spinach, ricotta, and nutmeg in a large bowl.

Step 5

To assemble, arrange 3 noodles lengthwise in the bottom of a greased 9x13 inch baking dish. Spread with 1/3 the ricotta mixture, 1/3 of the turkey mixture, and 1/3 of the mozzarella. Repeat layers, ending with remaining mozzarella. Bake in preheated oven for 25 minutes. Cool for 5 minutes before serving.