Creating Lemon Dijon Chicken Thighs with Caramelized Onions is straightforward if you follow these steps:

1. Prepare the Marinade: In a bowl, combine lemon juice, lemon zest, Dijon mustard, olive oil, garlic powder, salt, and black pepper. Mix well.

1. Marinate the Chicken: Place the chicken thighs in a large resealable bag or bowl. Pour the marinade over the chicken, ensuring it’s well-coated. Refrigerate for at least 30 minutes.

1. Cook the Onions: In a large skillet over medium heat, add a tablespoon of olive oil. Once heated, add the sliced onions. Cook for about 10 minutes until they soften, stirring occasionally.

1. Add Sugar: If you desire extra sweetness, sprinkle the sugar over the onions. Continue to cook for an additional 10-15 minutes until they caramelize and become a rich brown color. Remove the onions from the skillet and set aside.

1. Preheat the Oven: While the onions are cooking, preheat your oven to 400°F (200°C).

1. Sear the Chicken: In the same skillet, increase the heat to medium-high. Add the marinated chicken thighs skin-side down, searing them for about 5 minutes until golden brown.

1. Bake the Chicken: Turn the chicken over and place the skillet in the preheated oven. Bake for 25-30 minutes or until the chicken reaches an internal temperature of 165°F (75°C).

1. Combine with Onions: In the last 5 minutes of baking, return the caramelized onions to the skillet, allowing the flavors to meld together.

1. Rest the Chicken: Once done, remove the skillet from the oven and let the chicken rest for 5 minutes before serving.

1. Garnish and Serve: Sprinkle fresh parsley over the chicken for an added touch of color and flavor.