Begin by peeling and deseeding the English cucumber. Cut it into small, even dice and place it in a medium bowl. Sprinkle salt over the cucumber and gently toss. Allow it to sit for 10 minutes.

While the cucumbers sit, combine the low-fat Greek yogurt, crumbled feta cheese, chopped fresh herbs, lemon juice, grated lemon peel, and black pepper in a large mixing bowl. Mix until smooth and well blended.

After 10 minutes, drain the cucumbers in a fine mesh sieve and pat them dry with paper towels. Fold the drained cucumbers into the yogurt mixture.

On each slice of whole-grain bread, layer a handful of alfalfa sprouts followed by spoonfuls of the cucumber-yogurt filling. If desired, add thin slices of red onion. Top with another slice of bread.

Cut each sandwich in half diagonally and arrange them on a serving platter. Serve immediately to enjoy crispness.