Heat oven to 425 degrees.
In a skillet, cook sausage and onion over medium high heat until done. Drain off fat.
Add prepared marinara sauce and stir until combined. Turn off heat and set aside.
Cook ravioli per package directions.
In an oven proof 11 x 14 baking dish, spread on 1/3 up of sausage mixture.
Layer on cooked ravioli. Sprinkle shredded mozzarella cheese over pasta.
Spread another layer of sausage sauce over cheese. Place remaining ravioli in a single layer sauce. Ladle on remaining sauce.
Sprinkle remaining mozzarella cheese over dish.
In a small bowl, mix together panko bread crumbs and Parmesan cheese. Sprinkle over mozzarella cheese. Drizzle lightly with olive oil. Cover with foil and bake for 15 minutes.
Remove foil and continue cooking until ravioli bake is bubbling and slightly brown on top. Let rest for 10 minutes and serve.