Peel the skin and white membrane off the grapefruit and separate the pieces.
Reserve three grapefruit slices for the vinaigrette and squeeze the juice; set aside.
Chop up remaining grapefruit for the salad.
In a medium bowl whisk olive oil, squeezed grapefruit juice (from 3 slices of grapefruit), champagne vinegar, chopped shallots, salt and pepper.
Season scallops with salt and pepper.
Heat a large pan on a high heat.
When the pan is hot, add oil and place scallops in the pan.
Sear without touching them for a few minutes until the bottom forms a nice caramel colored crust.
Turn and cook about another minute while their centers are still slightly translucent (you can check this by viewing them from the side).
Be careful not to overcook.
Remove from the pan.
Divide the baby greens evenly between four plates.
Arrange grapefruit on the plate and top with scallops; drizzle with vinaigrette.