First, make the salsa. If you’re using papaya, cut it in half and scoop out all the small black seeds and discard them. Cut the papaya halves in half again, then slice off the peel. Cut the flesh into roughly 1cm (about ºin) dice and place the diced papaya flesh in a bowl.
If you’re using a mango, slice off the two ‘cheeks’ on the narrow sides of the stone and set aside. Then, using a peeler or a small fruit knife, remove the peel from the piece of mango that has the stone, and cut the flesh into 1cm (about ºin) dice and put in a bowl. Then, taking one of the mango ‘cheeks’ cut a grid of 1cm (about ºin) squares in the flesh, cutting down as far as the skin but not through it. Then, turn the cheek inside out so that it resembles (well, kind of!) a hedgehog, and cut off the cubes of mango flesh. Repeat with the other ‘cheek’ and place all the mango pieces in a bowl.
Trim off the base and the green top from the fennel bulb, reserving the fennel fronds for later. Peel off the outer piece of the fennel if it is at all brown or discoloured. Cut the trimmed fennel into 1cm (about ºin) dice and add it to the bowl of diced papaya or diced mango, whichever you’re using, along with the finely chopped red onion, the chopped fresh coriander, the lime juice, and the extra-virgin olive oil. Season to taste with salt and freshly ground black pepper. It should taste fresh and zingy. The salsa can sit for a few hours.
To pan fry the fish, first dry the fillets on kitchen paper then season them with salt and freshly ground black pepper. Heat a cast iron or non-stick frying pan on a high heat until it is very hot and smoking. Add a dash of extra-virgin olive oil, then immediately add the fish fillets. Cook them for just a few minutes, depending on thickness, on one side. Turn them over when they are golden on one side. Cook on the other side until they are just golden and opaque all the way through.
Serve with just a few spoonfuls of the salsa.