Preheat the oven to 180°C.
Heat the olive oil in a large casserole dish set over a medium heat. Sweat the onion and garlic for 5 minutes, stirring occasionally, then add the potato and continue to cook over a medium heat for 5 minutes. Add the wine and let it reduce by half. Add the chopped tomatoes, tuna steak and bay leaf. Cover loosely with aluminium foil and bake for 10 minutes.
Remove from the oven and stir through the peas. Cover again with aluminium foil and leave to rest for 5 minutes. Adjust the seasoning to taste, then discard the bay leaf. Spoon into a serving dish and serve immediately.