In a medium mixing bowl, combine the drained canned solid white tuna with ¼ cup of plain Greek yogurt, 1 tablespoon of extra-virgin olive oil, and the juice of half a lemon. Add 2 tablespoons of finely chopped shallot, 1 tablespoon of fresh chives, 1 tablespoon of fresh dill, ½ teaspoon of garlic powder, and freshly ground pepper to taste. Mix everything until creamy and well-blended, ensuring there are no large chunks remaining.

Take two slices of whole-wheat bread and spread the creamy tuna mixture generously on one side of each slice. Make sure the edges are covered so that the filling doesn't spill out when assembled.

Next, wash and thinly slice the Persian cucumbers into rounds, keeping them about ¼ inch thick for the perfect crunch. Place a generous layer of the cucumber slices over the tuna mixture on one of the slices of bread.

Carefully place the second slice of bread on top of the cucumbers, tuna-side down, and gently press down to help the layers adhere together.

Using a sharp knife, cut the sandwich diagonally into two halves. Serve immediately for the best freshness, perhaps alongside a side of fresh fruit or a light salad.