Homemade Smash Burger with Caramelized Onions & Burger Sauce
Thin beef patties smashed onto a blazing-hot skillet, cooked until deeply browned and crispy, stacked with melted cheese, sweet caramelized onions and a tangy homemade burger sauce.
What Makes a Smash Burger Different?
A smash burger is all about surface area. Instead of shaping the beef into thick patties before cooking, loosely rolled balls of ground beef are placed onto a screaming-hot skillet and immediately pressed into thin patties.
That contact with the hot metal creates the deeply browned, almost lace-like edges that make smash burgers so addictive. Stack two patties together with melted cheese and suddenly a handful of very simple ingredients becomes something far greater than the sum of its parts.
Ingredients
Homemade Burger Sauce
Stir together:
- ½ cup mayonnaise
- 2 tbsp ketchup
- 1 tbsp yellow mustard
- 2 tbsp finely chopped pickles or relish
- 1 tsp pickle juice
- ½ tsp smoked paprika
- ¼ tsp garlic powder
- ¼ tsp onion powder
- Small pinch of black pepper
Refrigerate while you cook the burgers. Ten or fifteen minutes of resting gives the flavors time to settle into each other.
First, Caramelize the Onions
Thinly slice the onions. Heat the butter and oil in a skillet over medium-low heat, then add the onions with a small pinch of salt.
Cook for approximately 15–20 minutes, stirring regularly, until the onions become soft, golden brown and jammy. Lower the heat if they begin browning too quickly.
Dark onions aren’t necessarily caramelized onions. Gentle heat creates sweetness; excessive heat creates burnt edges.
How to Make the Perfect Smash Burger
Divide the Beef
Divide the beef into 8 loose portions of approximately 85 g / 3 oz each. Gently roll each portion into a ball without compressing it tightly.
Get the Pan Very Hot
Heat a cast-iron skillet, carbon-steel pan or flat-top griddle over high heat until very hot. Avoid nonstick cookware for this technique because you want aggressive contact between the beef and the cooking surface.
Smash Immediately
Place two beef balls onto the hot skillet with plenty of space between them. Immediately press each one firmly using a sturdy metal spatula or burger press until very thin.
Season & Build the Crust
Season the exposed side with salt and black pepper. Cook without moving the patties for approximately 1½–2 minutes, until the edges become dark brown and visibly crisp.
Scrape, Flip & Cheese
Slide a sharp metal spatula firmly underneath each patty, scraping up the browned crust with it. Flip, immediately add cheese and cook for approximately another minute.
Stack Them
Place one cheese-covered patty directly on top of another to create a double smash burger.
Toast the Buns
Lightly butter the cut sides of the burger buns and toast them in the pan until golden.
Assemble
Spread burger sauce across the bottom bun. Add pickles, the double cheese-covered smash patties, caramelized onions and another spoonful of sauce before closing with the toasted top bun.
The Ideal Smash Burger Stack
6 Rules for Crispy Smash Burger Edges
A barely warm skillet gives you gray beef. High heat creates the crust.
Form loose beef balls rather than tightly compacted meatballs.
Press the beef immediately after it hits the cooking surface.
Don’t repeatedly press the burger after the crust begins developing.
Use a sturdy metal spatula and scrape firmly underneath before flipping.
Add cheese as soon as you flip so it melts while the second side cooks.
What Pan Should You Use?
Cast iron is ideal because it stores plenty of heat and gives the beef excellent contact with the cooking surface.
Carbon steel and a flat-top griddle also work beautifully. Stainless steel can work too, although the patties may require a little more confidence when scraping.
Avoid a delicate nonstick pan. Smash burgers are not a delicate operation.
Smash Burger Variations
Add pickled jalapeños and hot sauce to the burger sauce.
Add crispy bacon between the two patties.
Smash paper-thin sliced onions directly into the beef while cooking.
Add a restrained drizzle of hot honey over the crispy beef for sweet heat.
What to Serve with Smash Burgers
- Crispy French fries
- Air fryer potato wedges
- Sweet potato fries
- Pickles
- Onion rings
- Coleslaw
- Simple chopped salad
- Grilled corn
Frequently Asked Questions
What beef is best for smash burgers?
Ground beef with around 20% fat works particularly well because enough fat renders during cooking to produce flavorful, juicy patties and crisp edges.
Do I need a burger press?
No. A strong, flat metal spatula works well. If your spatula is flexible, place a second spatula or another sturdy kitchen tool on top to apply firm pressure.
Why isn’t my smash burger crispy?
The most common causes are a pan that isn’t hot enough, overcrowding, moving the patty before the crust forms or failing to press the beef thin enough at the beginning.
Can I cook smash burgers on a grill?
Yes, but you’ll need a flat griddle or cast-iron surface placed over the grill. Standard grill grates don’t provide enough surface contact to produce the signature crust.
Can I prepare the burgers ahead of time?
You can portion the beef into balls and prepare the sauce and onions ahead of time. For the best crust, however, cook and assemble the patties immediately before serving.
More Burger Recipes to Try
If you’re building a burger night, explore our other homemade burger recipes for chicken, beef and plant-based variations.
Homemade Smash Burger at a Glance
Two crispy-edged beef patties, two slices of melted cheese, caramelized onions, sharp pickles and creamy burger sauce inside a toasted bun.
Thin patties. Big crust. Zero restraint.
Food & Snacks 
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