1) Bung the potato in the microwave and cook for to 4.5 minutes. 2) Meanwhile, empty the salmon into a bowl and mix with the capers, cider vinegar, Tabasco and salt and pepper to taste. 3) Take the potato out of the microwave. Cut through with a cross and open. Add the butter and season. 4) Top the potato with the salmon mix. 5) Dress the watercress with the oil and lemon juice. Season to taste and serve alongside the potato.