Heat oil over medium heat.
Add onion, saute until soft.
Add wine and anchovy paste.
Boil until reduced to 3/4 cup.
Add tomatoes, with juice - bring to a boil.
Sprinkle fish with salt and pepper.
Add fish to skillet, reduce heat, cover and simmer until fish is cooked.
Remove fish. Add olives, oregano, orange peel, and increase heat to high.
Boil until sauce is thickened, 5 minutes or so. Serve fish with sauce and toasted bread.