Preheat oven to 350F.
Season the turkey breast on all sides with 2 teaspoons of the salt and 1/2 teaspoon of the pepper. Place the turkey in a small roasting pan or on a baking sheet, and roast for 30 minutes then brush the turkey with 2 tablespoons of the olive oil and continue to roast for another 30 minutes or until the thickest section register an internal temperature of 165F on an instant-read-thermometer.
Remove the pan from the oven and loosely tent it with aluminum foil. Let the turkey rest for at least 15-20 minutes. Once the turkey has rested, remove the breast bones and cut the turkey into thin slices. Reserve on a platter.
To make the Waldorf dressing, in a medium bowl, combine the chopped pecans with 1/2 cup yogurt, 1/4 cup mayonnaise, parsley and vinegar. Season with 1/2 teaspoon salt and 1/4 teaspoon pepper.
Halve and core the apple then cut it into thin slices on a mandoline. In a medium bowl, toss the apple slices with the lemon juice, celery and cherries. Add the dressing and toss.
In a small bowl, combine the remaining 2 tablespoons olive oil, 2 tablespoons yogurt, 2 tablespoons mayonnaise, 1/4 teaspoon salt and 1/4 teaspoon pepper. Mix well.
To assemble: Place 4 slices of toast on a clean work surface. Spread 1 tablespoon of the yogurt-mayonnaise mixture on each slice of toast. Top each one with lettuce leaves, several slices of turkey, 3/4 cup of the apple salad and 1/4 cup of sprouts. Top with the remaining slices of toast. Cut each sandwich in half, and serve immediately.