Make sauce: Peel and seed cucumber and place into a food processor or blender with one clove of garlic. Puree till smooth. Stir in sour cream or yogurt, cayenne and lemon juice. Season with salt and pepper. Spoon sauce over Gyro and enjoy. Shred iceberg lettuce and dice tomato, set aside. If youd like, place pita on grill to mark each side, (8-10 seconds). Begin assembling your Gyro, adding lettuce, Chicken and tomato. To jazz it up, try adding some cheese (cheddar or feta work well).