Heat the olive oil in a tagine or a casserole. Fry the meatballs until they brown. Remove them from the casserole. Fry the peppers in the cooking fat for 4 minutes.
Add the harissa to the bell peppers and fry gently for 1 min. Place the meatballs between the peppers and pour in the passata. Bring to the boil.
Turn down the heat and simmer the meatballs covered in 20 min.
Finely chop the coriander. Take the tagine from the heat. Add the coriander and season with pepper and salt.