Two 5-ounce cans chunk light tuna in water, drained
1/2 cup alfalfa sprouts
Cut the cucumbers in half lengthwise, scoop out the seeds and some of the flesh, and then toss the seeds and flesh. Make many fork pricks inside the hollowed-out cucumbers. In a medium bowl, combine the vinegar, mustard, 1/8 teaspoon salt, and a few grinds of pepper. Pour the oil in gradually while continuing to whisk until well combined. Apply some vinaigrette to the inside of each cucumber.
In the basin with the remaining vinaigrette, combine the yogurt, dill, celery leaves, mayonnaise, scallions, celery, lemon zest, 1/4 teaspoon salt, and a few grinds of pepper. Stir in the tuna after it has been drained.
Create the sandwiches by layering two cucumbers with tuna salad and 1/4 cup of sprouts each. With the remaining cucumbers, make a sandwich. Wrap each sandwich in wax paper after being cut in half (this will help catch all the juices).