Smashburger Sliders with Caramelized Onions and Melted Cheddar

By Lauren Mitchell, Test Kitchen Director · Reviewed by AislePrompt Editorial · Published 2026-06-20 · Updated 2026-06-20

Juicy mini smashburgers topped with sweet caramelized onions and sharp cheddar cheese, served on soft slider buns for a perfect bite. This american-inspired sandwiches & wraps ready in about 35 minutes pairs ground beef (80/20), divided salt, divided black pepper for a weeknight-friendly dinner that comes together with one pan and minimal cleanup. Each serving lands at about 350 calories and feeds 8, so it slots cleanly into a weekly meal plan and pairs well with a quick salad or grain on the side. Tap "Plan a meal with the AI" below to drop this recipe into your week and send the ingredients straight to Instacart. Nutrition values are approximate, calculated from USDA FoodData Central (fdc.nal.usda.gov) — verify against ingredient labels for any health-driven dietary plan.

Ingredients

• 1 lb ground beef (80/20)
• 1 tsp, divided salt
• 1/2 tsp, divided black pepper
• 2 medium, sliced thin yellow onion
• 2 tbsp unsalted butter
• 8 thin slices cheddar cheese slices
• 8 slider buns
• 2 tbsp vegetable oil
• 1/4 cup mayonnaise
• 1 tbsp dijon mustard
• 8 slices pickles
• 8 small leaves lettuce leaves
• 1 medium, sliced into 8 thin rounds tomato

Instructions

1. Step 1: Heat 2 tbsp unsalted butter in a large skillet over medium-low heat. Add 2 medium thinly sliced yellow onions and 1/2 tsp salt. Cook slowly, stirring occasionally, for 25-30 minutes until onions are deeply golden and caramelized.
2. Step 2: In a large bowl, gently mix 1 lb ground beef with 1/2 tsp salt and 1/4 tsp black pepper. Divide into 8 equal portions and form loosely into balls.
3. Step 3: Heat 2 tbsp vegetable oil in a cast iron skillet over medium-high heat until shimmering. Place 2-3 beef balls in the pan and immediately smash them down with a sturdy spatula to about 1/4-inch thickness. Cook for 2-3 minutes until edges are crispy.
4. Step 4: Flip each patty, season with a pinch of salt and pepper, and top each with a slice of cheddar cheese. Cook an additional 1-2 minutes until cheese melts and patties are cooked through.
5. Step 5: Toast 8 slider buns cut side down in a separate pan or under a broiler until golden.
6. Step 6: Mix 1/4 cup mayonnaise with 1 tbsp Dijon mustard. Spread this sauce on bottom buns, then layer with lettuce leaf, tomato slice, cheese-topped patty, caramelized onions, and pickle slice. Top with bun halves and serve immediately.