Drain crab on paper towel and break up the pieces with a fork. Place into a bowl, add â…“ cup of the mayonnaise to the crab with lemon zest, juice and chopped dill. Season with pepper, mix well. Cover and chill until required.
Spread the remaining mayonnaise on the bread pieces. Using a 4.5cm round cutter, cut 4 rounds from each slice of bread.
Top half the bread with the crab mixture, sandwich together with the remaining rounds. Garnish with thin slices of cucumber and salmon roe or black lumpfish caviar.