Peel the outer skin of the grapefruit with a knife. Insert the knife along the thin part of the skin and remove the fruit from the segments. Tear the fruit into bite-size pieces.
Squeeze the juice from the remaining thin skin and add the salt and pepper. Mix well and then slowly mix in the extra virgin olive oil little by little.
Wash the watercress and tear only the tender stems and leaves. Put the stems and leaves on a plate and place the grapefruit on top.
Pour the dressing from Step 2 on top and you're done.
Story Behind this Recipe
I believe I saw a recipe for grapefruit salad in a newspaper that used one grapefruit for the flesh and one grapefruit for the juice. I made my own version that only uses one grapefruit for both. When I saw some delicious looking watercress and grapefruit I tried making it.
It depends on the size of the grapefruit but use roughly the same amount of olive oil as the grapefruit juice, and then adjust according to your taste. It's OK for a little of the flesh from the fruit to be left inside the segment as you want to get some juice from the grapefruit. If it's a big grapefruit, it's fine to use half of the grapefruit for the flesh and the other half for the juice.