How to Make It
Preheat the oven to 350°. In a small saucepan, melt the butter with the maple syrup and 2 teaspoons of coarsely ground pepper. Remove the glaze from the heat.
On a large heavy-duty rimmed baking sheet, toss the sliced onions with the olive oil. Season the onions with salt and pepper and spread in an even layer. Season the chickens inside and out with salt, then arrange them on top of the onions. Loosely tie the chicken legs together with kitchen string.
Roast the chickens for 45 minutes. Brush the chickens all over with half of the maple glaze and continue roasting them for 1 hour longer. Increase the oven temperature to 425°. Generously brush the chickens with the remaining glaze and roast for 15 minutes longer, or until the cavity juices run clear and the chickens are richly browned.
Transfer the chickens to a platter and let rest for 10 minutes before carving. Pour the onions and pan juices into a large glass measuring cup and skim the fat from the surface. Season with salt and pepper and serve with the chickens.