Preheat the oven to 180oc/350 Fahrenheit/gas 4
Peel off the skins of the chorizo and dice.
Heat an oven safe pan over a medium-high heat and add the chorizo (no oil needed)
Cook the chorizo for about 3 minutes to release its oil, then add the red onion and stir to coat. (See note if using fresh or cooking chorizo)
Cook for 2-3 minutes until the onion is just starting the soften, then add the tomatoes and garlic and stir.
After 2 minutes, add the beans and a dash of salt and pepper and stir again.
If you are using frozen fish then add it now - nestle into the sauce and season well on top.
Put the pan in the oven, uncovered, and cook for 15 minutes.
Take out the oven and flip the fish over with a spatula or tongs, re-nestle into the sauce and season the other side. if you are using fresh cod then season both sides and add to the sauce now.
Place back in the oven and cook for another 12-15 minutes, until the cod is cooked through. The juices from the tomatoes, onions and chorizo should have made a delicious sauce.
Scatter with fresh chopped parsley and serve with a big green salad and rice or some baby new potatoes (or whatever else you fancy!)