Heat your oven to 325 degrees
Remove excess (but not all) fat and silver skin from the beef shank
Cut deep slits into the beef shank all over
Mix the spices together and rub them all over the shank, pressing the spices into the slits.
Line a roasting pan with high sides (at least 2 1/2 to 3 inches high) with aluminum foil (this is optional but it makes cleanup much easier)
Slice the onion into 1/3 inch rings and place them in the bottom of the roasting pan
Place the beef shank on top of the onion slices.
Cover the entire top of the pan with foil sealing the sides all around to keep the steam in
Cook the shank for 4 1/2 to 5 hours until the shank is tender
Remove the foil and turn the oven temperature up to 450 degrees
Roast uncovered for 10 minutes, turning once to get all sides browned.
Strain the juices and pour through a fat separator and serve with the beef shank and braised onions