For the chicken: Place the chicken on a baking sheet and allow the chicken to sit at room temperature for 1 hour.

Preheat the oven to 450 degrees F and place a 12- or 13-inch nonstick cast-iron pan in the oven to heat.

Pat any excess moisture from the skin of the chicken. Brush the butter all over the surface of the chicken. Sprinkle with 1 tablespoon celery salt on the surface and 1 teaspoon celery salt in the cavity. Sprinkle the entire surface well with salt and pepper.

Stuff the cavity with the thyme, rosemary and as much of the quartered lemon as will fit.

Remove the pan from the oven, then carefully distribute the onions in the pan; drizzle with the white wine and sprinkle with salt, pepper and a bit of celery salt. Arrange the chicken in the center.

Roast the chicken until it is deep golden brown and caramelized, about 40 minutes, then turn off the oven and allow to rest in the off but warm oven until the thickest part of the leg registers 160 degrees F on a thermometer, about 20 minutes.

Allow the bird to rest for 20 minutes (the temperature will continue to rise to 165 degrees F out of the oven). Carve and serve with the onions and sauce over the top of each piece of chicken. Garnish with parsley if desired.

For the potatoes: Meanwhile, place the potatoes in a medium pot with 1 tablespoon plus 1 teaspoon salt and cover with water by 1 inch.

Bring the water to a boil, then lower to a simmer and cook until potatoes are fork-tender, 12 to 25 minutes.

Transfer to a large bowl. Using the back of a wooden spoon, smash the larger potatoes a bit so they soak up the dressing. You can also tear a few in half. While the potatoes are hot, pour over the lemon juice and segments, the olive oil and plenty of salt and pepper.

Toss to coat the potatoes, then add half the arugula and toss again. The heat from the potatoes will cook the arugula, so add the second half of the arugula just before serving. Season again as needed with olive oil, salt and pepper.