Preheat oven to 400 degrees F and grease a baking pan with the olive oil. Place the salmon pieces in the pan and bake for 8 to 10 minutes. Meanwhile, cook eggs in boiling water for 5 minutes, then plunge into cold water and peel. Blend soft-boiled egg with watercress, lemon juice, and seasonings, and refrigerate until ready to serve. When salmon is done, serve hot with egg dressing poured over the top.