To create the Ladolemono (lemon vinaigrette), juice the Lemon (1) into a large bowl, discarding the seeds.
Stir in the Dijon Mustard (1 tablespoon), Fresh Oregano (1/2 tablespoon), Salt (1/4 teaspoon) and Ground Black Pepper (1/4 teaspoon).
Slowly whisk in Olive Oil (2 tablespoon) and reserve the rest for plating.
Pat dry the Chicken Breast (2) with paper towels and place in the bowl with the Ladolemono. Cover with plastic wrap and refrigerate for one hour.
Cut the Mini Cucumber (1) in half lengthwise and then into 1/4 inch dice and place in a medium bowl.
Mince the Garlic (2 clove) and add to the cucumber. Remove the stems from the Fresh Dill (0.25 ounce) and discard stems. Finely chop the dill and add to the bowl.
To the bowl with the cucumber mixture, stir in the Greek Yogurt (150 gram), White Wine Vinegar (2 tablespoon), Salt (1/4 teaspoon) and Ground Black Pepper (1/4 teaspoon) until all ingredients are combined. Refrigerate until ready to use.
Cut the Lemon (1) into 4 wedges and hold for plating.
Cut the Hothouse Beefsteak Tomato (1) and Red Onion (1) into 1/2-inch slices and set aside. Peel the Red Bell Pepper (3 ounce) and cut into 1/4-inch slices and place in another medium bowl.
Drizzle the onions with Olive Oil (1 tablespoon), toss, and set aside. Wrap the Pita Bread (2) in foil.
When the time for the chicken is almost up, preheat the grill or grill pan over medium high heat.
To prevent sticking on the grill, use Vegetable Oil (to taste) to oil the grill grates. Grill the chicken breasts on each side for 4 minutes. Place the onions on the grill, season with a pinch of Salt (to taste) and Ground Black Pepper (to taste).
Cook until charred and softened, about 4 minutes. Place the wrapped pita bread on the grill for about 30 seconds, until warmed through.
Cut the chicken into 1/2-inch cubes. Spread a spoonful of the Ladolemono down the center of each warm pita. Arrange the chicken pieces on top, followed by the onions, tomatoes and pepper slices, dividing them equally.
Season each with a pinch of Salt (to taste) and Ground Black Pepper (to taste) and top with the Arugula (2 ounce) and Olive Oil (4 tablespoon).
Spoon the tzatziki over the arugula and garnish with lemon wedges and serve and enjoy!