Heat the oven to 200°C/Fan 180°C/Gas 6. Rinse and trim the aubergine. Finely chop the flesh into 1 cm cubes. Pop in a roasting tin.
Season with salt and freshly ground black pepper. Drizzle with olive oil. Toss to mix, then roast for 25-30 mins till soft. Fill the kettle and boil it.
Peel and finely chop the onion. Peel and grate or crush the garlic. Rinse the oregano and pat them dry. Strip the leaves from the stalks.
Heat a drizzle of olive oil in a deep frying pan or wok. Add the mince and onion to the pan. Season. Cook over a medium heat for 5 mins till the mince is browned. Stir occasionally to break up the mince.
Add 1 tsp of the cinnamon, the garlic and half the oregano to the pan. Stir and fry for 1 min. Stir in the tomatoes. Half fill the empty tin with water. Add to the pan. Bring to the boil. Simmer, without the lid on, for 15-20 mins till the sauce has thickened.
Fill a pan with water. Add a pinch of salt. Bring to the boil. Add the penne. Cover. Simmer for 8 mins till the pasta is tender but not too soft.
Take the aubergine out of the oven. Stir into the tomato sauce. Taste and adjust the seasoning. Drain the penne. Stir the penne into the sauce. Serve in bowls sprinkled with the rest of the oregano.