Begin by cooking the jumbo pasta shells according to package instructions until al dente. Drain and set aside to cool slightly.
In a large mixing bowl, combine ricotta cheese, egg, lemon juice, salt, garlic powder, onion powder, dried basil, dried oregano, and black pepper. Mix until creamy and well combined.
Using a spoon or piping bag, carefully fill each jumbo shell with the ricotta mixture, packing each shell generously.
Spread about 1 cup of marinara sauce evenly on the bottom of a 9x13 inch baking dish. Arrange the stuffed shells in a single layer over the sauce. Pour the remaining marinara sauce over the shells.
Sprinkle shredded mozzarella cheese generously over the top of the sauce-covered shells.
Cover the baking dish with aluminum foil sprayed with cooking spray. Bake in a preheated 375°F (190°C) oven for 25 minutes. Remove foil and bake for an additional 15 minutes until cheese is bubbly and golden.
Remove from oven and let sit for a few minutes. Garnish with minced parsley if desired, then serve warm and enjoy.