Preheat your oven to 375°F (190°C).
Cook the jumbo pasta shells in a large pot of boiling water until al dente, then drain and set aside to cool slightly.
In a non-stick skillet over medium heat, cook the ground turkey until fully browned and crumbled, then set aside.
Place the baby spinach in a steamer basket or skillet with a splash of water and cook until wilted; squeeze out all excess liquid and finely chop.
In a medium mixing bowl, combine the cooked ground turkey, chopped spinach, fat-free ricotta, liquid egg whites, garlic powder, dried oregano, sea salt, and black pepper.
Spread half of the marinara sauce evenly across the bottom of a small oven-safe baking dish.
Stuff each cooked pasta shell with a generous portion of the turkey and ricotta mixture and arrange them in the baking dish.
Spoon the remaining marinara sauce over the shells and sprinkle the grated parmesan cheese on top.
Cover the dish with foil and bake for 20 minutes, then remove the foil and bake for an additional 5 minutes until the sauce is bubbly and the cheese is melted.