Heat olive oil in a nonstick skillet. Add the diced onion along with a pinch of the salt and pepper. Sauté for about 5 minutes, stirring occasionally, until the onion becomes fragrant.
Add the minced garlic and cook for about 1 minute. Stir in the ground turkey and Italian seasoning, then continue cooking until the turkey is no longer pink.
Pour in 1 jar of marinara sauce, approximately 2 cups, and mix until combined. Take the skillet off the heat and set the meat sauce aside.
Prepare the ravioli according to the package instructions, usually by boiling for 4-5 minutes. Drain, rinse under cold water, and toss with 1-2 Tbsp. olive oil to keep the ravioli from sticking. Set aside.
In a medium bowl, combine the ricotta, egg, chopped parsley, and chopped basil.
Preheat the oven to 375°F. Assemble the lasagna in a 9×13-inch baking dish in the following order: spread 1 cup marinara sauce evenly over the bottom, add an even layer of ravioli, spread over all of the meat sauce, add another ravioli layer, spread over the ricotta mixture, add a third ravioli layer, cover with the remaining marinara sauce, and finish with the shredded mozzarella.
Loosely tent the baking dish with aluminum foil, keeping the foil from touching the cheese as much as possible. Bake for 30 minutes covered, then remove the foil and bake for another 25 minutes. If desired, broil for 2-3 minutes at the end, until the mozzarella is melted and bubbling.
Allow the lasagna to cool slightly before serving. Parmesan cheese and additional fresh basil or parsley may be added when serving if desired.