Dice 2-3 English cucumbers into small pieces, toss with salt, and let drain in a colander for 10 minutes.

In a mixing bowl, combine yogurt, feta cheese, fresh herbs, lemon zest, lemon juice, and black pepper.

Pat dry the cucumbers and fold them into the yogurt mixture.

Toast the bread until golden brown, about 2-3 minutes per side.

Layer sprouts on one slice of toast, spread the cucumber salad mixture, add onion slices if desired, and top with another slice of bread.

Cut sandwiches in half diagonally and serve immediately.