To make the roulade, place the salmon fillet on a board, and using a sharp knife, cut through the centre horizontally. Butterfly the fish so that you can open it like a book.
Cover the fish in a piece of plastic wrap and very gently use a mallet to pound out the flesh so that it is about a six millimeters thick.
Season the fish with salt and pepper and using a fresh sheet of plastic wrap or tin foil, roll the fillet into a tight round cylinder. Tie ends with string if needed.
Place in the refrigerator for one hour to set.
Make the sauce.
Preheat the oven to 325˚F (160˚C).
Heat two tablespoons (30 milliliters) canola oil in a pan. Slightly soften the chopped onion. Add wine, salt, pepper, cream, and lemon juice, and let it reduce by half.
Just before serving add cayenne pepper, cherry tomatoes, crabmeat, chopped parsley to the pan and stir. Cook just until warmed through about 45 seconds.
In a bowl, combine paprika, thyme, oregano, garlic powder, salt, and pepper.
Remove the salmon roulade from the fridge and discard the wrapper.
Using a wet knife, slice the salmon into four pieces (about 150 grams each).
Dip the flat ends of each piece into the spice mixture.
Heat one tablespoon (15 milliliters) oil in a skillet at medium-high heat and sear the salmon flat side down for 30-60 seconds to create a crust. Do this on both sides.
Place seared salmon onto an oiled baking sheet, and heat in the oven for four minutes.
Remove salmon from oven and plate. Spoon sauce over top. Garnish with fresh parsley.