Spray a skillet with nonstick cooking spray and heat until hot over high heat.
Add the chopped onion and green bell pepper and cook for 3 minutes, stirring occasionally.
Add the ground turkey and sauté until browned and cooked through, about 5 minutes. Stir frequently.
Add the Italian seasoning, diced tomatoes (with the juice from the can) and the tomato sauce; stir to combine and bring to a boil while stirring occasionally. Remove from heat and season to taste with salt and pepper.
In a bowl mix together cottage cheese or ricotta, 8 ounces of shredded mozzarella and chopped spinach. Stir together and season with salt and pepper. Add a pinch of nutmeg (optional).
Spray pan with nonstick cooking spray and spread 1 cup of the sauce (from Step 5) across the bottom of pan.
Add 4 lasagna noodles on top of the sauce. Spread 1/2 of the cottage cheese mixture (from Step 6) or ricotta mixture over the noodles
Top with 4 more lasagna noodles, spread 3 cups of the tomato sauce (from Step 5) over noodle layer.
Repeat Step 8 and top with the remaining 4 noodles. Top with the remaining sauce and remaining mozzarella cheese.
Place lasagna pan on a cookie sheet in the oven to prevent it from bubbling over onto the oven floor.
Bake at 400 degrees F for 45 minutes until hot and bubbly. Let pan cool 5-10 minutes before cutting and serving.
Storage: The lasagna can be stored in the fridge for 2 days or in the freezer for up to a week.