Preheat your Ninja Woodfire oven on Gourmet Roast mode. Press the Woodfire Flavor button and add wood pellets. Meanwhile, place the chicken in a baking dish or on a tray, or in a cast iron Dutch oven. Slice the onions into rings and add them around the chicken. Place a bit of margarine on top of the chicken. Season with salt and pepper.

Roast until the chicken and onions are golden brown. While roasting, peel the potatoes and cut them into wedges. Remove the dish from the oven and arrange the potatoes around the chicken, mixing them well with the onions.

Switch to Max Roast mode to brown the chicken even more. Press the Woodfire button again to add wood pellets for wood-fired cooking. Watch closely, as it will brown quickly. Set to 535°F (280°C) and roast until nicely golden.