In a small bowl, whisk together olive oil and balsamic vinegar, reserve. In a large bowl, combine watercress and lettuce. Divide among twelve salad plates. Place two to three grapefruit sections on lettuce. Sprinkle salad with pomegranate seeds, feta and honey walnuts. Drizzle with olive oil and balsamic vinegar.
In a small fry pan over medium heat, sauté walnuts until hot, about 1 to 2 minutes, stirring constantly. Drizzle with honey, quickly stir, and remove from heat. Sprinkle with salt. Transfer nuts to a plate to cool.