Sloppy Onion Smash Burger Recipe on Stove

There’s just something about a good smash burger that hits differently—crispy edges, juicy center, and all that flavor packed into every bite.

Now toss in a layer of sweet, caramelized onions and you’ve got a next-level onion smash burger that’s ridiculously good.

Cooking it right on the stove keeps things simple and brings that diner-style vibe straight to your kitchen.

Get ready to make a burger that’s crave-worthy, messy in the best way, and totally satisfying.

Servings: 2 burgers
Prep Time: 10 minutes
Cook Time: 15-20 minutes
Total Time: 30 minutes

Ingredients

For the Onion “Buns”:

• 1 large yellow onion (cut into ½-inch thick slices, keep whole rounds intact)
• Salt and pepper (to taste)
• 1 tsp sugar (optional, helps with caramelization)
• 1 tbsp olive oil or butter

For the Smash Patties:

• ½ lb ground beef (80/20)
• Salt, pepper, and garlic powder (to taste)
• 2–4 slices American cheese

For the Special Sauce:

• 2 tbsp mayonnaise
• 1 tbsp ketchup
• 1 tsp yellow mustard
• 1 tsp sweet relish
• ½ tsp white vinegar
• ¼ tsp sugar
• Pinch of paprika (optional)

Instructions

• Heat a skillet over medium heat and add olive oil or butter.
• Add the thick onion slices, sprinkle with salt, pepper, and optional sugar.
• Cook for 5–7 minutes per side, until golden and soft, flipping carefully to keep the rings intact. Set aside.
• In a small bowl, mix together mayonnaise, ketchup, mustard, relish, vinegar, sugar, and paprika.
• Stir until smooth and refrigerate until ready to use.
• Divide ground beef into 4 equal balls.
• Heat a skillet or griddle over high heat until very hot.
• Place a beef ball on the surface and smash it flat with a spatula (use parchment paper between the spatula and meat to prevent sticking).
• Season with salt, pepper, and garlic powder.
• Cook for 1.5–2 minutes until edges are crispy, then flip.
• Immediately add a slice of cheese to each patty and cook for 30 more seconds. Remove from heat.
• Start with one onion round as the base.
• Add a smash patty with cheese.
• Spoon some special sauce on top.
• Add another patty, more sauce if desired.
• Top with another onion round.
• Serve immediately while hot and juicy.
• Optional: Wrap in parchment or serve with pickles on the side.

Tips

• Make it spicy: Add sriracha to the sauce.
• Add crunch: Top with shredded lettuce or crispy bacon (though that breaks the pure onion-bun version).
• No onion buns? Wrap in lettuce for another low-carb option.