1. 1) Slice half of the onion into strips and the zucchini into rounds.
2. 2) In a drizzle of olive oil, sauté half of the onion with the zucchini. Season with salt and pepper. Cook until the zucchini is softened but still slightly firm.
3. 3) In a drizzle of olive oil, sauté the other half of the onion without browning it, then add the ground meat. Season with salt and pepper to taste.
4. 4) Once the ground meat is cooked (starting to separate), add the cartons of cream and tomato sauce. Season with salt and pepper again.
5. 5) Simmer until the mixture thickens slightly.
6. 6) Remove the zucchini from the heat and transfer them to a baking dish using a slotted spoon to drain any excess water.
7. 7) Once the mixture has thickened, pour it over the zucchini and sprinkle with grated gruyère cheese. Bake at 425°F until golden and bubbly.