Preheat oven to 400°F.
In a large ovenproof skillet, heat the oil over medium heat. Add ground beef and cook until it's browned, about 5-7 minutes.
Meanwhile, combine the tomatoes, carrots, onion, and garlic in a food processor and chop until coarsely ground.
When the meat is browned, pour off any fat. Add the tomato mixture, chicken stock, ricotta (or cottage cheese), and spinach (optional). Stir thoroughly.
Bury the uncooked lasagna noodles in the sauce, and sprinkle the mozzarella evenly over all.
Bake the lasagna uncovered until the cheese is melted and bubbling, 10 to 15 minutes.
Remove the pan from the oven and let stand uncovered for 10 minutes. Serve warm.