Melt the butter over medium-high heat in a large skillet. Place the sugar in a shallow dish and dredge the chuck in it until nicely coated on all sides. Reserve the remaining sugar and set aside. Set the meat in the hot skillet and season with salt and pepper. Cook about 15 minutes, browning on all sides. When browned, stir in the sherry vinegar and cook for 1 minute. Add the cranberries, reserved sugar, and orange zest. Add a pinch of cayenne, and pour in the orange juice. Stir well, reduce heat to low, and cover. Cook at a low, gentle simmer for 2 hours or more, until tender, stirring the meat every 30 minutes or so. Taste and adjust the seasoning if needed.

Remove from heat, and allow to rest for a few minutes. Carve, and serve with the sauce.