Shape the beef into 4 patties. Season well with pepper.
On the grill
Fire up your grill for direct cooking 400 - 450 F.
Pour the soup into a pan and place on the grill near the direct heat so it begins to warm.
Grill burgers as desired but do not cook completely. When they reach around 140 F remove from the direct heat and transfer to the hot French onion soup.
Continue cooking the burgers in the soup until they reach 165 F.
Remove the patties and place on the bun bottoms.
Top with cheese and bun tops.
Serve with soup on the side for dipping, if desired.
On the stovetop
Heat a large skillet over medium-high heat.
Add the burgers and cook on both sides until medium rare, around 140 F.
Spoon out any fat from the skillet and stir in the soup.
Continue to cook the burgers in the hot soup until they reach 165 F, another 5-10 minutes.
Remove the patties and place on the bun bottoms.
Top with cheese and bun tops.
Serve with soup on the side for dipping, if desired.