Crab-and-pink Grapefruit Salad

• 6 individual dishes (serving)
• 3 pink grapefruit
• 2 heads butter lettuce
• 1 shallot
• 260 gr crab meat picked over to remove bits of cartilage (cooked)
• 120 ml olive oil
• 16 ml wine vinegar (white)
• 16 ml balsamic vinegar
• 4 gr grapefruit peel (grated)
• 1 gr salt