Wash, halve, stem and seed the peppers, and cut into very fine long thin slices. Peel the onion, halve through the root, and cut into thin lengthwise slices. Film a large frying pan with the oil, add heat for 4 to 5 minutes while you add the garlic, herbs and seasonings. Vegetables should be partially cooked; they will finish with the fish. May be done in advance to this point; let cool uncovered, then transfer to a bowl, cover and refrigerate. Cut the fish into serving chunks. Just before you are to saute it, season all sides with a sprinkling of salt and pepper, dredge lightly in flour, and shake off excess. Into a second frying pan (or in the same one, if you have done the vegetables ahead), pour in enough oil to film it and set over moderately high heat. When very hot but not smoking, add the fish in one layer. Saute for 2 minutes, then turn and saute for 2 minutes on the other side-not to brown, merely to stiffen slightly. Spread the cooked vegetables over the fish. Pour in the wine and broth-enough to come halfway up the fish. Cover and simmer about 10 minutes. Fish is done when it has turned from springy to gently soft-it needs a little more cooking than other fish, but must not overcook and fall apart. Arrange fish and vegetables on a hot platter and cover. Rapidly boil down the juices in frying pan until almost syrupy, then spoon them over the fish, and serve, surrounded by the optional tomato fondue.