Dressing: stir the shallot, lemon juice and salt in small bowl and let stand at room temperature 30 minutes. Then add the oil with a small whisk.
Cut the peel and pith from the grapefruits and take the segments out of the membranes and cut in half...put on paper towels to drain...ok, this was a little time-consuming, but worth it.
Cut the lobster tail in half and slice
Divide the grapefruit, avocado and lobster on among the salad plates
Top each mixture with a handful of the greens and drizzle with the dressing. Sprinkle lightly with sea salt (and pinenuts if desired) and serve right away.