This variation on the orange and poultry marriage is perfect for one of those Sunday nights in February. I’m thinking of one when the winter vegetables have begun to all taste the same and you’re craving flavors that will warm you up, electrifying your sense of taste and smell. The acidity of the orange juice in this sumptuous braise, paired with the depth of flavor that ancho chiles deliver, are a potent combination.
Preheat the oven to 450 degrees.
Rub the chicken with peanut oil, season with kosher salt, to taste and set out on the countertop for 30 minutes or so to take the chill off before cooking.
Using your fingers, gently slide a bay leaf under the skin on each side of the breast. Cut 4 of the kumquats lengthwise into thin slices and push them under the skin next to the bay leaves.
Heat 1 tablespoon peanut oil in a 12-inch or larger cast-iron frying pan or a 5-quart larger Dutch oven over medium heat. Add the onion, chile powder, cumin seeds, and ¼ teaspoon salt and sauté for 3-5 minutes.
When the onion is soft and just beginning to brown on the edges, scrape out the spices and onion to a plate and set aside. Set the chicken in the hot pan and brown on the sides and bottom, 8-10 minutes. Return the onion-spice mixture to the pan, pour in the orange juice and stock, and tuck the remaining kumquats around the chicken.
Put the chicken in the oven and roast for 30 minutes before either inserting an instant-read thermometer into the thickest part of a thigh or cutting into the thigh with a paring knife. The thermometer should register 175 degrees. (If using a knife, look for clear, not red or pink, juices running from the spot where you pierced the meat and opaque, barely pink flesh at the bone.) If the chicken isn’t done, roast for 5 or 10 minutes longer and check it again.
When the chicken is done, remove it from the pan and let rest. Using a slotted spoon, transfer the onion and kumquats to a small bowl. Pour the liquid from the pan into a fat separator. (You can also use a heatproof jar and use a spoon to skim off as much fat as you can.) Return the defatted liquid to the pan and simmer over medium heat until reduced by ½. (You may skip this step if you have very little liquid left — this will depend on your chicken, your pan, and your oven.) Return the onion and kumquats to the sauce and stir briefly, just to heat them.
Arrange the orange slices in a circle on a large platter and place the chicken on top. Pour the sauce over the bird. Carve the chicken at the table, serving each person 1 hot orange slice to begin their plate.