1/4 cup fresh lemon juice, plus 1 lemon—peeled, seeded and diced
1/4 cup water
1 tablespoon Dijon mustard
1/4 cup finely chopped parsley
2 skinless, boneless chicken breast halves (about 7 ounces each)
3/4 pound Yukon Gold potatoes, peeled and cut into 3/4-inch dice
2 tomatoes, cut into 1-inch dice
1 small sweet onion, such as Vidalia, cut into 1/2-inch dice
1 garlic clove, minced
2 tablespoons snipped chives
2 thyme sprigs
2 tablespoons extra-virgin olive oil
Salt and freshly ground pepper
In a small glass baking dish, combine the lemon juice with the water, mustard and 2 tablespoons of the parsley. Add the chicken and turn to coat. Cover and let stand at room temperature for 1 1/2 hours.
Meanwhile, preheat the oven to 400°. In a medium baking dish, toss the potatoes with the diced lemon, tomatoes, onion, garlic, chives, thyme, 1 1/2 tablespoons of the olive oil and the remaining 2 tablespoons of parsley. Season with salt and pepper. Bake the potatoes for about 40 minutes, or until tender.
Preheat the broiler. Transfer the chicken breasts to a small baking sheet and brush with the remaining 1/2 tablespoon of olive oil. Season with salt and pepper and broil 8 to 10 inches from the heat, turning once, until golden and cooked through, 12 to 14 minutes. Transfer to a cutting board and let rest for 5 minutes. Broil the potatoes for about 2 minutes, or just until golden. Thinly slice the chicken. Spread the potatoes on plates, top with the chicken and serve.