Prepare the cucumber

• Wash the cucumber and slice it lengthwise into thin ribbons with a peeler.
• Pat the ribbons dry and lay them side by side, overlapping, on a sheet of paper or a board.

Make the tuna filling

• Drain the tuna and place it in a bowl.
• Add the mashed avocado, Greek yogurt, lemon juice and Dijon mustard.
• Season with salt and pepper and mix until creamy.

Roll and serve

• Spread the tuna mixture over the cucumber ribbons.
• Roll the cucumber tightly into a log and slice into pieces.