How to Make It
Preheat oven to broil with rack 9 inches from heat. Place a 12-inch cast-iron skillet on stove-top over medium-high. Add beef; cook, stirring often, until browned, 8 to 10 minutes. Remove beef; drain and set aside. Wipe skillet clean.
Heat oil in skillet over medium-high; add onion, and cook, stirring occasionally, until tender, 8 to 10 minutes. Add garlic to skillet; cook, stirring constantly, until fragrant, about 1 minute. Stir in crushed tomatoes, stock, Italian seasoning, salt, pepper, and ravioli. Bring to a boil; reduce heat to medium. Cover and simmer until ravioli are tender, about 8 minutes. Uncover and return cooked beef to skillet. Stir in half of spinach, and cook just until wilted. Repeat with remaining spinach. Top with mozzarella and Parmesan.
Broil in preheated oven until cheese is melted and golden, about 6 minutes. Remove from oven, and garnish with fresh basil.