Sprinkle chicken with 1/4 teaspoon salt and 1/8 teaspoon pepper. Combine chicken, 1 1/2 teaspoons oil, juice, and Dijon in a bowl; toss to coat. Let stand 4 minutes. Heat a grill pan over medium-high heat. Coat pan with cooking spray. Add chicken to pan; grill 5 minutes on each side or until done. Place chicken on a cutting board. Cut chicken into 1/4-inch-thick slices.
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Combine remaining 1/4 teaspoon salt, remaining 1/8 teaspoon pepper, remaining 2 tablespoons oil, shallots, vinegar, and honey in a large bowl, stirring with a whisk to dissolve honey. Add tomatoes and lettuce; toss to coat. Place 1 1/2 cups salad mixture on each of 4 plates; top evenly with sliced chicken.