Preheat your oven to 375°F (190°C).

In a boiling pot, cook the jumbo pasta shells until they are al dente, about 8–10 minutes. Drain and set aside.

In a skillet, heat olive oil over medium heat. Sauté onion and garlic for 3–4 minutes until translucent.

Stir in fresh spinach and cook for an additional 2 minutes until wilted. Remove from heat and cool slightly.

In a mixing bowl, combine ricotta, cream cheese, shrimp, crab meat, half of the mozzarella, salt, black pepper, and red pepper flakes. Mix well.

Spread half of the marinara sauce in the bottom of a baking dish.

Stuff each shell with the seafood mixture and arrange in the baking dish.

Pour remaining marinara sauce over the shells and top with the rest of the mozzarella and grated Parmesan.

Cover with foil and bake for 25 minutes, then remove foil and bake for an additional 10 minutes until cheese is bubbly.

Allow to cool slightly before serving. Enjoy!