Preheat oven to 425 Fahrenheit.
Cut chicken thighs into about 1 inch pieces. Toss chicken with oil, lemon juice, and seasonings.
Place seasoned chicken on a greased sheet pan and bake for 15-20 minutes or until chicken is cooked through.
In a large pan over medium heat, add 1 tablespoon butter, 1 cup pearl couscous and 1 ¼ cups water. Stir until butter is melted. Cover and set to low, cook for 12 minutes.
Uncover couscous, stir in 1 tbsp more butter, juice of ½ lemon, and 2–3 big handfuls of spinach. Stir until the spinach is wilted.
Make the sauce: Mix together 2 tablespoon Greek yogurt, 1 tablespoon mayonnaise, ½ tablespoon lemon juice, and ¼ teaspoon garlic powder and ¼ teaspoon salt to make the sauce.
Fill individual bowls with couscous and chicken mixture and drizzle with lemon yogurt sauce to serve.