Preheat your oven to 375°F (190°C).
In a skillet over medium heat, brown the ground beef until fully cooked, then drain any excess fat.
Season the beef with sea salt, black pepper, and garlic powder, then stir in the fresh spinach until it wilts.
Pour the marinara sauce into the skillet with the beef and spinach, stirring to combine, then remove from heat.
In a small mixing bowl, whisk together the part-skim ricotta cheese, egg white, and dried oregano until the mixture is smooth and creamy.
Boil the lasagna noodle in salted water until al dente, then drain and cut into three or four equal pieces to fit your baking dish.
In a small oven-safe dish, layer a spoonful of the meat sauce, followed by a piece of noodle and a layer of the ricotta mixture.
Repeat the layers until all ingredients are used, finishing with a final layer of meat sauce and a sprinkle of parmesan cheese.
Bake for 20 minutes until the cheese is melted and the edges are bubbling and golden.