Discard the skin of the salmon, and cut it into 4 equal steaks. Sprinkle each steak with salt and black pepper, pressing it firmly into the steaks with your hand. Coat lightly in oil, and refrigerate until ready to cook.
Rub the yellow pepper with a little vegetable oil, and grill or roast until the skin is well blistered. Allow to cool, and then peel off the charred skin, remove the seeds, slice into 8 pieces, and place in a bowl. Cut the tomatoes into 6 wedges each, and slice the new potatoes if they seem very large.
Combine all the vegetables, season lightly with salt and pepper, and toss with the olive oil, and parsley. Leave to come to room temperature. To make the dressing, combine all the dressing ingredients in a blender, and pulse until smooth and emulsified.
To cook the salmon, heat a large grill pan, (preferably cast iron) over high heat until almost smoking. Add the salmon, and sear for 1-3 minutes on each side. To serve, divide the vegetables among the plates, and place a salmon steak in the centre of each. Surround with a generous drizzle of the dressing, and serve at once.