There’s nothing better than tangy pickled jalapeños — except maybe a burger topped with them. This burger gets extra heat from the jalapeños mixed into the beef and the pepper jack cheese melted on top. Make the pickled jalapeños at least a day in advance for the best flavor.
Bring the vinegar, water, salt, and sugar to a simmer in a small sauce pan. As soon as the sugar and salt are dissolved, remove the pan from the heat and pour the brine over the sliced jalapeños . Store (in a covered jar) in the refrigerator overnight.
Combine the ground beef and chopped pickled jalapeños and mix, just until combined. Gently form the beef into 4 patties and then season each patty with salt and pepper.
Grill the burgers, about 5 minutes per side, until they reach an internal temperature of 160 degrees F. Add one slice of cheese to each patty and grill for one minute more.
Serve the burgers on the toasted buns, topped with more jalapeños , red onion slices, and lettuce.