Lightly spray the salmon with the avocado oil spray.
Season with salt and black pepper.
Heat a cast-iron pan, large enough to fit both pieces of salmon over a high heat for about 1 minute.
Generously spray the pan with the avocado oil spray.
Place the salmon into the pan, skin side up and sear for about 1 minute.
Using a spatula, carefully turn the salmon over onto the skin side.
Add the tomatoes around the fish and sprinkle with the chopped tarragon.
Finally add the butter in two pieces to each side of the pan.
Place the pan into the oven and roast for 8-10 minutes.
Serve at once with your choice of side and garnish with more chopped tarragon
The salmon I used was about 2 inches wide and 1½ inches tall. If your salmon is thinner, it will cook faster. Try and buy center pieces and not from the tail end. You can usually tell it's ready by gently pressing the thickest part with a finger - it should feel slightly firm. It will cook fast and keep cooking even after you take it out of the oven. It's always better to take it out early and not overcook it.