Wash and dice the English cucumber. Place in a bowl, sprinkle with salt, and let sit for 10 minutes.

In a separate bowl, mix together Greek yogurt, crumbled feta, dill, chives, lemon juice, lemon peel, and black pepper until smooth.

Drain the cucumbers using a fine mesh sieve and pat dry. Fold them into the yogurt mixture.

On slices of whole-grain bread, layer alfalfa sprouts and cucumber filling, optionally adding red onion.

Cut sandwiches into halves or quarters and serve immediately.