2. Pat the fish dry with a paper towel. Mix together the onions and the capers.

3. Over high heat, heat vegetable oil in a small ovenproof skillet (preferably cast iron) until it is very hot. Place the filet, skin side down, in the pan and cook about 1 minute, until it browns. Using a spatula, turn the filet and cook a minute or two on the other side.

4. Off the heat, season the filet with salt and pepper, and spoon the onion/caper mixture on top (the skinless side). Pour the vermouth or wine over the fish. Cook in the oven until the thickest part of the filet looks opaque, about 10 minutes.