In a large skillet, heat the olive oil over medium heat.
Dice the onion and mince the garlic. Saute onions and garlic in the oil until soft and translucent, about 4-5 minutes. Remove from heat.
In a large mixing bowl, combine the pasta sauce, onions, garlic, dried herbs and salt.
Layer the casserole in a 8x8 baking dish: Spread a layer of sauce, then arrange the raviolis in a single layer, followed by mozzarella cheese and Parmesan cheese. Repeat the layers until all ingredients have been used.
Cover with aluminum foil. Bake, covered, for 20 minutes. Remove the foil and bake for another 20 minutes, until golden brown and bubbly.