Shape the ground beef into four evenly sized patties, about 1.5 cm thick, and set aside.
Heat your grill or skillet over medium-high heat, and place the patties on once hot, hearing a satisfying sizzle.
Cook the patties for about 4 minutes on each side until browned and slightly charred, then top each with a slice of cheese.
Cover the skillet or close the grill lid to help the cheese melt beautifully, about 1 minute, until gooey and bubbling.
While the burgers cook, peel and thinly slice the onions, then caramelize them in a pan over medium heat until golden and sticky, about 15 minutes.
Using carving knives and spoons, carefully carve spooky faces into the small pumpkin, creating eyes, nose, and a jagged mouth for a festive look.
Slice the tomato and wash the lettuce leaves, preparing all toppings for assembly.
Lightly toast the burger buns on the grill or in a toaster, about 2 minutes, until golden and crisp.
Assemble each burger by placing a lettuce leaf and tomato slice on the bottom bun, then add the beef patty with melted cheese.
Gently set the carved pumpkin face pieces on top of each burger, creating a spooky face design.
Finish by topping with the other half of the bun, then garnish with caramelized onions and a drizzle of spicy ketchup or mustard.
Serve immediately, marveling at your spooky, cheesy Jack O’ Lantern burgers that are as fun to look at as they are to eat!
