In a small bowl, combine the mayonnaise, lime juice, garlic powder, and a pinch of salt. Mix until smooth and refrigerate.

Slice the jalapeños in half, remove the seeds if you prefer a milder flavor, and finely dice them.

Divide the ground beef into four equal portions and gently roll each into a loose ball without compacting the meat.

Heat a cast iron skillet or heavy-bottomed pan over medium-high heat until very hot.

Butter the cut sides of the buns and toast until golden brown.

Place one beef ball onto the hot skillet and immediately smash it into a thin patty using a sturdy spatula. Season with salt and pepper.

Cook for 2–3 minutes until the edges become deeply browned and crispy.

Flip the patty, top with a slice of pepper jack cheese and a generous sprinkle of diced jalapeños. Cook for another 2 minutes until the cheese melts.

Spread the jalapeño mayo over both toasted buns.

Assemble the Flavorful Jalapeño Popper Smash Burgers by placing each patty onto the bottom bun. Add lettuce, tomato, onions, or pickled jalapeños if desired, then finish with the top bun.

Serve immediately while hot.