Combine beer, ketchup, and cranberry sauce in a medium bowl and set aside.

Set the instant pot on sauté mode “high” and add the olive oil. Salt and pepper the brisket and brown it on both sides - about three minutes per side. Remove brisket.

Turn sauté down to “normal” and add sliced onions to pan. Brown the onions, stirring frequently for about 3-5 minutes.

Place brisket on onions – layering it as needed, then pour beer mixture over brisket. Close the lid and turn it on to “pressure cook” for 60 minutes.

When 60 minutes is up, let it natural pressure release (NPR) for 10 minutes, then let it quick release for about four minutes or until the silver knob goes down.

At this point, the meat should be almost tender. Remove and slice it across the grain (crucial to cut against the grain or it will be tough to chew even if it is cooked properly)