2 teaspoons olive oil
1 red onion, halved, sliced
8 chicken thighs, trimmed
1 teaspoon salt
Freshly ground pepper
1/4 cup orange juice
3 tablespoons balsamic vinegar
1 bunch arugula (about 4 cups) or baby spinach, coarsely chopped

Heat oil in a large skillet over medium-high heat; add onion. Cook
until it begins to soften, about 4 minutes. Remove from skillet; keep
warm.
Season chicken with salt and pepper; transfer to skillet. Cook,
turning, until brown on both sides, about 4 minutes per side. Pour
orange juice and vinegar over chicken. Cover; reduce heat to simmer.
Cook until chicken is cooked through, about 20 minutes. Remove chicken
from skillet; keep warm.
Increase heat to high; add arugula to skillet. Cook, stirring,
until it just begins to wilt; about 2 minutes. Remove from heat. For
each serving, place some arugula in a bowl; top with 2 chicken thighs.
Top with onions.