In a very small saucepan, simmer champagne and shallot until reduced to 2 tablespoons, this will take less than five minutes. Off heat stir in salt and butter, cover and set aside.
Heat oil in a 10 inch sauté pan over high heat until almost smoking.
Pat scallops very dry. Sprinkle with salt and add to pan.
Cook without disturbing for two to three minutes until very golden brown.
Add butter to pan, and swirl pan to distribute butter around scallops.
Turn scallops over and cook until just opaque about 1-2 minutes. This will depend on the size.
Spoon champagne butter on the plate, top with scallops and scatter grapefruit over.