HEAT 12-inch cast-iron skillet on stove-top over medium-high heat. ADD beef; COOK, stirring often, until browned, 8 to 10 minutes. REMOVE beef; DRAIN; SET ASSIDE. WIPE skillet clean.

HEAT oil in skillet over medium-high; ADD onion; 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.

PREHEAT oven to broil with rack 9 inches from heat.

UNCOVER and return cooked beef to skillet. STIR IN half of spinach; 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, GARNISH with fresh basil.