There’s nothing better than a smashburger with melty cheese, jammy caramelized onions, and a generous swipe of special sauce. This caramelized onion smashburger is gloriously messy in all the right ways — a thin, craggy patty with crispy edges, sweet buttery onions, toasted brioche, and sauce that drips down your wrist. It’s the kind of burger that elevates weeknight meals and shines at backyard cookouts.
FEATURED COMMENT
“We made this tonight. It was so flavorful! We cooked the burgers in our pizza oven. My husband said the burgers were restaurant quality. We will definitely be making this again. Served it with corn on the cob and homemade garlic potato wedges.”
– LAURA M.
★★★★★
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Erica’s Thoughts
I love a great burger, and once I started making smashburgers at home, they became a regular in my weeknight rotation. A smashburger’s thin patty and crisped edges deliver intense beef flavor and a perfect texture that a thicker patty just can’t match.
Key takeaways for this caramelized onion smashburger:
- Ultra-thin, craggy patties infused with a buttery, savory mixture prevent dry, bland burgers.
- A punchy special sauce is essential — here it’s a simple, creamy blend of mayo, ketchup, Worcestershire, horseradish and garlic.
- Shredded lettuce works better than whole leaves for balance and texture.
- Classic dill pickle chips pair perfectly; use what you like for your own twist.
- Even picky eaters love a smashburger — the texture and melty cheese make it irresistible.
Smash a ball of beef on a screaming hot flat top or heavy skillet, watch the edges crisp into golden lace, then crown it with American cheese. Add buttery toasted brioche, a generous portion of caramelized onions and lots of special sauce and you’ve got a next-level burger that’s simple to make and endlessly satisfying.
What You’ll Need to Make Caramelized Onion Burgers
Ground beef: 80/20 is recommended for juicy smashburgers.
Butter + Worcestershire + Smoked Paprika: Mixed into the beef for savory richness.
Kosher salt: Salt the patties at the grill for the best crust and texture.
Sweet onions: Vidalia or other sweet onions caramelize beautifully; yellow or white work too.
Avocado oil + butter: Butter for flavor and oil for a higher smoke point while caramelizing onions.
Brown sugar + balsamic vinegar: These boost caramelization and deepen the onions’ sweetness.
Brioche buns: Buttery, soft buns are ideal — toast them for extra flavor.
American cheese: The classic melt for smashburgers.
Toppings: Tomato slices, shredded lettuce, pickles, and optional bacon or jalapeños.
Special Sauce: A quick mix of mayo, ketchup, horseradish, Worcestershire, mustard, garlic, smoked paprika and hot sauce yields a creamy, tangy sauce that ties the burger together.
How to Make this Caramelized Onion Burger Recipe
Prep the patties
Melt butter and whisk in Worcestershire and smoked paprika. Add the mixture to the ground beef and gently combine with your hands until just mixed. Divide into four balls and chill briefly while you prepare the onions and other components.
Caramelize the onions
Heat avocado oil and butter in a large skillet or flat top over medium-low. Add thinly sliced onions and toss to coat. Stir in brown sugar, balsamic and a pinch of salt. Cook low and slow, stirring often, until the onions are deeply golden and jammy — about 20–25 minutes total. Keep the heat moderate so they don’t burn.
Smash the patties
Turn heat to medium-high. Place a beef ball on the hot surface, sprinkle with kosher salt, cover with a small square of parchment and press quickly with a heavy spatula or grill press until very thin. Cook 2–3 minutes until edges are deeply browned and craggy, flip, add a slice of American cheese, and cook 1–2 minutes more until melted.
Whisk up the sauce
Combine mayo, ketchup, prepared horseradish, Worcestershire, mustard, grated garlic, smoked paprika and a few dashes of hot sauce. Taste and adjust salt or heat as desired. This creamy sauce adds tang and richness to the burger.
Assemble the burgers
Toast brioche buns (butter and warm in a 400°F oven for a few minutes). Build the burger: bottom bun → large spoonful of special sauce → caramelized onions → cheesy smashed patty → tomato → pickles → shredded lettuce → another spoonful of sauce → top bun. Serve immediately while the cheese is melty and the patty is crisp.
Summer grilling at its very finest — caramelized onion burger for the win.
Expert Tips
- Low and slow for the onions — keep the heat moderate so they caramelize instead of burning.
- Use a small square of parchment paper when smashing so the patty doesn’t stick to the press or spatula.
- Chill the beef balls briefly before smashing to help them hold together.
- Don’t overmix the meat or the patties will be tough — combine just until incorporated.
- Salt the patties on the hot grill rather than mixing salt into the raw meat for a better crust and juicier interior.
- American cheese melts perfectly on smashburgers; freshly sliced from the deli is a nice touch.
- Avoid too-lean meat — 80/20 is my preference for flavor and juiciness.
FAQs
80/20 ground chuck is my go-to — it gives good flavor and enough fat to crisp nicely.
Yes. Caramelized onions keep in the refrigerator for 3–4 days. Rewarm gently before using.
Use a heavy cast-iron skillet, stovetop griddle, or an indoor grill pan to caramelize onions and smash the patties. A flat surface with even heat works best.
Salt mixed into raw meat draws out proteins and can make the mixture tacky and dense. Salting on the grill seasons the exterior, preserves juiciness, and helps form a flavorful crust.
A large, flat metal spatula works — press quickly and firmly to flatten the patties.
Use gluten-free buns and confirm your Worcestershire and other condiments are gluten-free.
What to Serve With These Burgers
Crispy air-fryer fries, sweet potato fries, potato chips, or a bright summer salad pair nicely. These sides keep the meal classic and satisfying.
Need a fast way to win friends? Juicy, flavor-packed burgers are an obvious answer.
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Caramelized Onion Burger Recipe
5 from 3 reviews
- Author: Erica
- Prep Time: 15 minutes
- Cook Time: 30 minutes
- Total Time: 45 minutes
- Yield: 4 smash burgers
- Category: Dinner
- Method: Grill
- Cuisine: American
Description
Juicy caramelized onion burgers with melty cheese, special sauce, and buttery brioche buns. Easy and beyond delicious — the ultimate homemade smashburger.
Ingredients
Equipment you need:
- parchment paper
- grill press or a heavy, flat spatula
- flat top grill, indoor grill pan, or a large heavy-bottomed skillet
Patties
- 1 lb ground beef (80/20 preferred)
- 2 tablespoons butter
- 1 tablespoon Worcestershire sauce
- 1 teaspoon smoked paprika
- kosher salt, to season on the grill
Caramelized Onions
- 2 sweet onions, thinly sliced
- 1 tablespoon avocado oil
- 1 tablespoon butter
- 2 teaspoons brown sugar
- 1 tablespoon balsamic vinegar
- pinch of salt
Special Sauce
- 1/2 cup mayo
- 2 tablespoons ketchup
- 1 teaspoon prepared horseradish
- 1 teaspoon Worcestershire sauce
- 1 teaspoon yellow mustard
- 1 clove garlic, grated (or 1 teaspoon garlic paste)
- 1/2 teaspoon smoked paprika
- dashes of hot sauce or sriracha, to taste
- pinch of salt, to taste
Assembly
- 4 brioche buns, toasted
- 4 slices American cheese
- Toppings: thinly sliced tomatoes, shredded lettuce, pickles, special sauce
Instructions
- Patties part one: Melt 2 tablespoons butter and mix in 1 tablespoon Worcestershire and 1 teaspoon smoked paprika. Combine gently with the ground beef and form four balls. Chill while you prepare the onions.
- Onions: Heat 1 tablespoon avocado oil and 1 tablespoon butter over medium-low. Add sliced onions and cook until softened, about 10 minutes.
- Add 2 teaspoons brown sugar, 1 tablespoon balsamic and a pinch of salt. Continue to cook low and slow, stirring frequently, until deep golden and jammy, about 10–15 more minutes. Remove to a bowl.
- Patties part two: Increase heat to medium-high. Place each beef ball on the hot surface, sprinkle with kosher salt, cover with a parchment square and smash with a heavy spatula or press until very thin. Cook 2–3 minutes until edges are browned, flip, add cheese and cook 1–2 minutes more.
- Assembly: Whisk the sauce ingredients together and adjust seasoning. Toast brioche buns. Build: bottom bun, a big spoonful of sauce, caramelized onions, cheesy patty, tomato, pickles, shredded lettuce, more sauce, top bun. Serve immediately.
Invite friends — these burgers disappear fast.
Notes
Cooking thoughts: If you don’t have a flat top, a large cast-iron pan or indoor grill pan will work for both the onions and the burgers. A flat, hot surface gives the best crust. If you lack a grill press, a sturdy metal spatula pressed firmly works well enough.
Refer to the recipe photos for step-by-step visuals and the FAQ section above for tips.
Nutrition
- Serving Size: 1 smash burger
- Calories: 638
- Sugar: 10.5 g
- Sodium: 658.5 mg
- Fat: 42 g
- Carbohydrates: 29.7 g
- Fiber: 1.9 g
- Protein: 34.7 g
- Cholesterol: 115.7 mg