Steps
1. In a small bowl, mix Greek yogurt, lemon juice, dill, salt, and pepper.
2. Spread the Greek yogurt mixture on one side of each slice of bread.
3. Layer the grilled chicken, feta cheese, cucumber, tomatoes, and red onion on one slice of bread.
4. Top with the second slice of bread.
5. Heat a skillet over medium heat and lightly coat with cooking spray.
6. Place the sandwich in the skillet and cook until bread is toasted and cheese is melted, about 3-4 minutes on each side.
7. Remove from the skillet, cut in half, and serve.