To make the dressing, place all the ingredients in a small pot. Bring to the boil, then turn down the heat to a simmer and reduce until the sauce thickens. It should coat the back of a spoon. This can be made while the salmon is cooking.
To cook the salmon, heat the rapeseed oil in a heavy-based frying pan. Allow the oil to get very hot. Season the salmon with sea salt, then place it in the pan, flesh side down. This will give it a nice crust on the outside and moist texture on the inside. Cook for 4 minutes, then carefully turn the salmon over and cook the other side for 2 minutes.
To serve, place the salmon on a platter, spoon over the dressing and sprinkle with the toasted sesame seeds. Serve with a salad, baby potatoes and lime wedges.