Instructions
Cut the chicken breast into 4 English-muffin-sized portions.Place the chicken pieces between parchment paper and pound them to approximately ¼-inch thickness.In a bowl, combine the orange juice, lemon juice, lime juice, vinegar, water, oil, sugar, salt, onion powder, garlic powder, paprika, black pepper, and cayenne.Add the chicken to the marinade and refrigerate for at least 30 minutes. Do not marinate for longer than 4 hours.Preheat the oven to 350°F (180°C).Lightly coat an 8-inch square baking dish with nonstick cooking spray.Whisk the egg whites with ¼ teaspoon salt, then pour them into the prepared baking dish.Bake for 15–18 minutes, or until the center of the egg whites is just set.Allow the egg-white layer to cool for about 3 minutes, then cut it into 4 equal squares.Heat a grill pan or skillet over medium-high heat.Remove the chicken from the marinade and discard the remaining marinade.Cook the chicken for approximately 3–4 minutes per side, or until the thickest part reaches 165°F (74°C).Let the chicken rest for about 2 minutes while you lightly toast the English muffins.Place one grilled chicken portion on each English muffin bottom.Top each piece of chicken with one egg-white square and one slice of American cheese.Add the muffin tops.For softer sandwiches and better-melted cheese, loosely wrap the warm sandwiches in parchment paper or foil for about 2 minutes before serving. 
