For the salmon, heat half of the olive oil in an ovenproof frying pan and fry the fish skin-side down for 2-3 minutes, or until crisp and golden-brown. Lay the lime slices over the fish, sprinkle with the sugar, season with salt and freshly ground black pepper and place into the oven to roast for 5-7 minutes, or until cooked through.
For the peas, cook the peas in boiling water for 2-3 minutes, or until tender. Drain, then mash with the butter and lime juice and season with salt and freshly ground black pepper.
To serve, spoon the mushy peas onto a serving plate and lay the salmon over the top.