• Using a serrated knife, trim crusts from bread. Cut each bread slice into 2 (2½-x-1½-inch) pieces. Set aside.
• Trim ends from cucumber, and cut into 1½-inch sections. Slice each section vertically to yield 1½-x-⅛-inch pieces. Set aside.
• In a small bowl, combine mayonnaise, lemon zest, lemon juice, and salt, whisking until combined. Spread ¼ teaspoon mayonnaise mixture onto each bread piece. Top with 3 cucumber slices, evenly overlapping.
• Garnish with watercress, if desired.
*We used Pepperidge Farm White Sandwich Bread.
†We used Hellman’s Mayonnaise.
MAKE-AHEAD TIP: Prepare canapés up to 4 hours before serving, cover with damp paper towels, and refrigerate in an airtight container.