Preheat your oven to 375°F (190°C).
In a non-stick skillet over medium heat, brown the turkey sausage until fully cooked, breaking it into small crumbles as it sears.
Cook the whole grain lasagna noodles in a pot of boiling water until al dente, then drain and break into smaller pieces to fit your baking dish.
In a small mixing bowl, combine the ricotta cheese with the dried oregano, garlic powder, sea salt, and black pepper.
Spread 2 tablespoons of the marinara sauce on the bottom of a small, single-serve oven-safe baking dish.
Place a layer of noodles over the sauce, then spread half of the ricotta mixture, half of the cooked sausage, and half of the baby spinach.
Repeat the layer with noodles, the remaining ricotta, sausage, and spinach, then top with the final noodle pieces and the remaining marinara sauce.
Sprinkle the shredded mozzarella cheese evenly over the top.
Cover the dish with foil and bake for 15 minutes; remove the foil and bake for an additional 10 minutes until the cheese is melted and golden.