Peel the eggplant and sliced it into sticks about 3cm thick. Place in a colander and sprinkle all over with salt. Cover with a plate to weigh them down and let them express their moisture for 2 hours.
Heat 200ml of the olive oil in a heavy pot. Add the garlic and saute one minute. Add the onion and cook until transparent. Add the chopped capsicum and celery to the pot and cook until softened. Add the tomato paste and cook, stirring well to prevent sticking. Add the tomatoes and cook 30 minutes. If you like a fine-textured sauce, you can now blend it with an immersion blender. Season with salt, pepper and basil.
Rinse the eggplants and pat dry with paper towels. Cut into cubes. Heat the remaining 100ml olive oil and fry the eggplant until golden. Add to the sauce.
Cook the penne until al dente and serve with the sauce and grated ricotta.