Prep the cucumbers. Rinse and pat dry. For English cucumbers, cut each in half lengthwise. Use a spoon to gently scoop out the seeds, creating shallow “boats.” If using Persian cucumbers, halve them lengthwise and scoop a small channel.

Salt lightly and rest. Sprinkle a small pinch of salt inside the cucumber boats. Let them rest cut-side down on a paper towel while you make the tuna salad. This helps draw out excess moisture and keeps the filling from getting watery.

Drain and flake the tuna. Open the cans, drain well, and use a fork to break up the tuna into small flakes in a mixing bowl.

Make the dressing. Stir together mayonnaise (or Greek yogurt), Dijon mustard, and lemon juice until smooth. Add a small pinch of salt and pepper. Taste and adjust the lemon or mustard for brightness.

Add the crunch. Fold in diced celery, minced red onion, and chopped dill or parsley. If you like briny flavor, add a teaspoon of capers or chopped pickles.

Combine and season. Mix the dressing into the tuna until evenly coated. Taste and adjust salt, pepper, and acidity. A dash of paprika or hot sauce adds warmth without overpowering the freshness.

Fill the boats. Pat the cucumber halves dry. Spoon the tuna mixture into each boat, gently pressing so it stays put. Don’t overfill—aim for a clean mound down the center.

Finish with a topper. Add a sprinkle of fresh herbs, black pepper, or everything bagel seasoning. A small drizzle of olive oil gives a glossy finish if using yogurt.

Serve right away. Enjoy as-is or chill for 10–15 minutes for extra crispness.