Mix the salt, pepper and cayenne together in a small bowl. Set aside until needed.

Start the court bouillon by measuring the water and rice vinegar into a skillet large enough to hold the fish. Add the sliced vegetables and thyme, then cover the skillet with a lid and bring to a steady simmer. Cook for at least 10 minutes.

While the court bouillon is simmering, gently rinse the fish under cool water and remove the heads. Season the fish inside and out with the seasoning blend. You won't need all of the seasoning.

When ready to begin poaching, open the fish and place it skin side up into the court bouillon. It doesn't have to be submerged and you can cook several at the same time, depending on the size of the pan. (You don't have to open the fish if there's no room in the skillet. In that case, turn the fish about halfway through to cook both sides evenly.)

Cover the skillet with a lid and cook for 7 - 8 minutes until the fish is just cooked through. You should be able to see the flesh has changed color and texture.

Gently remove the fish to a platter to rest while you make the sauce.

Strain the court bouillon and measure a 1/2 cup of the liquid (You should have a little extra.)

Return the liquid to the skillet and begin whisking in the butter, a piece at a time. Whisk constantly over low heat to prevent the butter from browning. Season to taste with salt and pepper (I used some of the remaining seasoning.)

To serve, carefully arrange the trout on a plate and spoon the sauce over top. It's not a big deal if the trout breaks apart while moving it. It's just prettier if you can manage to keep the shape.