Heat a pot over medium high heat. Add ground beef and onions. Cook until meat is browned. Drain off fat if needed.
Add crushed tomatoes, both diced tomatoes, 2.5 tsp. kosher salt, garlic powder, 1 tsp. black pepper, and Italian seasoning. Bring to a boil then reduce heat to simmer and cook for 10 minutes. Remove from heat.
Mix ricotta, sour cream, 1/4 tsp. black pepper, and 1/2 tsp. kosher salt together in a small bowl. Set aside
Assemble lasagna in 3 layers using a 9 x 13 baking dish.
Spray baking dish with non stick cooking spray. Add 1/2 cup meat sauce and spread evenly on the bottom. Lay 4 lasagna noodles over sauce, overlapping a little. Spread 1/3 of the ricotta mixture evenly over noodles. Evenly distribute 1/3 of the cooked spinach. Add 1/3 of the meat mixture and spread evenly. Sprinkle some cheddar and parmesan then repeat layers 2 more times.
Cover the baking dish with aluminum foil. Bake in a pre-heated 375 degree oven for 45 minutes. Remove foil and top with reserved cheddar and parmesan. Continue to cook for 10 minutes until cheese is melted and browned.
Allow to rest for 10 minutes before cutting.
*May substitute sausage, ground turkey or ground chicken.