How to Make It
Combine 2 1/4 cups water and quinoa in a saucepan over high heat; bring to a boil. Cover. Boil 10 minutes. Drain and rinse under cold water. Drain; spread on paper towels to dry.
While quinoa cooks, heat a large skillet over medium-high heat. Add 1 tablespoon oil. Sprinkle chicken with 1/4 teaspoon salt and 1/4 teaspoon pepper. Add chicken to pan; cook 2 minutes on each side. Let stand 5 minutes. Cut chicken into thin slices.
Combine 2 tablespoons oil, remaining 1/4 teaspoon salt, remaining 1/4 teaspoon pepper, lemon juice, and mustard in a bowl; stir with a whisk. Add tomatoes; toss to coat.
Combine cooked quinoa, arugula, and basil in a large bowl. Add remaining 1 tablespoon oil; toss. Divide quinoa mixture among 4 plates. Top with chicken, tomato mixture, and pistachios.