Heat the olive oil in a non-stick frying pan and sweat the onion until soft but not coloured.
Add the chopped garlic and chilli and cook for one minute.
Add the chopped romero red pepper, brown sugar, red wine vinegar and red wine and bring to the boil.
Simmer until the liquid is syrupy and has reduced by half.
Season with salt and freshly ground black pepper.
Coat the tuna in olive oil and fry for two minutes on both sides, or until cooked to your liking.
To serve, spoon the chilli jam onto a serving plate and top with the tuna.