Lemon Chicken with Thyme

3 tbsp flour
1/2 tsp salt
1/4 tsp pepper
4 skinless, boneless chicken breast halves (1 pound total)
2 tbsp olive oil
1 medium onion
1 tbsp margarine
1 cup chicken broth
3 tbsp lemon juice
1/2 tsp thyme
lemon wedges (optional)
1 tbsp chopped parsley (optional)

1. In a plastic or paper bag, combine the flour, salt and pepper and shake to mix. Add the chicken and shake to coat lightly. Remove the chicken and reserve the remaining seasoned flour.
2. In a large skillet, warm 1 tbsp of the oil over medium heat. Add the chicken and brown on one side, about 5 minutes. Add the remaining oil, turn the chicken and brown well on the second side. Transfer the chicken to a plate and set aside.
3. Coarsely chop the onion. Add the margarine to the skillet. When it melts, add the onion and cook two or three minutes until softened, stirring constantly.
4. Stir in the reserved flour and cook, stirring, until the flour is completely blended, about 1 minute.
5. Add the broth, 2 tablesppons of the lemon juice and the thypme, and bring the mixture to a boil, stirring constantly.
6. Return the chicken to the skilet, reduce the heat to medium-low, and cover the skillet. Cook until the chicken is tender and opaque throughout, 5 - 10 minutes.
7. Divide the chicken among 4 plates. Stir the remaining 1 tbsp lemon juice into the sauce in the skillet, then pour over the chicken.
8. Garnish the chicken with lemon wedges and a sprinkling of parsley if desired. Serve with steamed vegetables and lightly buttered pasta.