In a skillet, saute onion and garlic in olive oil over medium high heat until soft and translucent. Set aside to cool.
In a large bowl combine meat, eggs, breadcrumbs, mozzarella and Parmesan, red pepper flakes, salt, pepper, 1/4 cup marinara sauce, 1/4 cup chicken broth, and 1 tablespoon chopped basil. Mix gently until fully combined, Spoon about 1/4 inch of marinara sauce on bottom of bread-size casserole dish. Fill casserole dish with meatloaf mixture. Pat gently on top to level.
Cook at 375 degrees for one hour. Remove from oven. Spoon the remaining marinara sauce over top of the meatloaf. Sprinkle with 1 tablespoon of fresh basil. Layer slices of mozzarella over top of basil. Return to oven for 20 minutes or until cheese has melted.
Allow meatloaf to cool for 5 minutes before serving.