In a mini food processor, process the thyme, fennel seeds, 1 tbsp salt, and 1 tbsp pepper until finely ground.
Place the olive oil in a small glass measuring cup, stir in the herb mixture, and set aside.
Add the onion and garlic to the cast iron skillet along with the lemon slices.
Place the chicken on top of the onion, skin side down, and brush with about half the oil mixture.
Using paper towels, pat the skin side of the chicken dry, and then brush the mixture of oil and herbs all over it.
Roast the chicken for 30 minutes in the preheated oven. Add the wine to the pan and roast for another 10 to 15 minutes, or until a meat thermometer registers 155 to 160 degrees.
Once the chicken has been cooked, remove it from the oven, sprinkle it with lemon juice, cover the skillet tightly with aluminum foil, and allow it to rest for about 10 to 15 minutes before slicing it into pieces.
Slice the chicken into quarters or eighths, sprinkle it with salt, and serve it hot with the pan juices, cooked lemon, and onions. Enjoy!