Cut off both ends of 3 inch diameter cans and spray interior lightly with pam. Clean and pick through the crab to remove bits of shell leave claw and large leg segments intact.

Use a large knife on the oranges to cut off both ends and then the rest of the peel including the pith and thin white outer membrane. Remove orange segments by cutting between the inner membranes with a pairing knife over a bowl-set aside along with accumulated juice; reserve the thick membranes that connect the segments. repeat with the grapefruit.

Cut the butter lettuce into thin 1/4 inch shreds.

Assemble

Cut the avocado in half, cut into small dice and sprinkle with lemon or grapefruit juice and salt to avoid discoloration. Dress the lettuce with a little vinaigrette. Place a can in the middle of each plate. divide the lettuce among the cans and compress. Follow with a layer of blood orange and grapefruit segments, gently compressing the layers with the back of a spoon. Do the same with the avocado and then the crab.

Gently un-mold the salad using a spoon to help push it out of the can. Top the crab with a dollop of the mayonnaise and chives. Place a large piece of crab on top of each salad.

Drizzle vinaigrette around the plate along with dots of blood orange juice and segments.