1 Wash the eggplants, remove their stem, and cut them lengthwise into slices (1 cm thick). Place them on a baking sheet lined with parchment paper, brush them with olive oil, and season with salt and pepper.
2 Broil in the oven for 5 to 10 minutes. Watch out to ensure that the eggplant slices don’t burn, and turn them over when they are golden brown. Repeat the process with the remaining vegetables, as 3 eggplants represent about 2 batches.
3 In a large casserole, heat 2 tablespoons of olive oil. Sauté the chopped onion and garlic over medium heat for 3 minutes. When they are translucent, add the tomato pulp, concentrate, chopped parsley and cumin. Salt and pepper to your liking.
4 Let simmer for 20 minutes covered, then 5 minutes uncovered. You can continue with your batches of eggplants while the sauce simmers. Add the ground beef to the sauce, stir and let cook for another 5 minutes.
5 In a large gratin dish, put a layer of grilled eggplants on the bottom, then a layer of meat in sauce, a second layer of eggplants, then a second layer of meat. Finish with a layer of eggplants. Pour the beaten eggs mixed with lemon juice over the dish, and sprinkle with a little grated gruyere cheese.
Finally, bake at 210°C (thermostat 7) for 10 minutes, or until the eggs are cooked and the cheese is melted and slightly browned.