Combine the onion, carrot, bell pepper, Scotch bonnet, vinegar, water, and allspice in a saucepan.
Bring to a simmer, cook for 3 minutes, then remove from the heat and let the vegetables steep.
Fry the fish:
Season the fish with lime juice, salt, and pepper. Dredge lightly in flour.
Heat the oil in a large skillet and fry the fish until deeply golden and cooked through, about 5 to 7 minutes per side depending on thickness. Drain on a rack.
Serve:
Place the fish on a platter and spoon the warm escovitch vegetables and vinegar over the top. Serve with rice and peas.
Notes
Use gloves when handling Scotch bonnet peppers.
For a milder pickle, remove the pepper seeds before slicing.