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Grass-Fed Beef Burger Patties with Avocado, Pickled Onion, and Sweet Potato Buns

Grass-Fed Beef Burger Patties with Avocado, Pickled Onion, and Sweet Potato Buns

The sweet potato bun is the move that changed burger night in our house. Cut a large sweet potato into thick rounds, roast until just tender with caramelized edges, and suddenly you have a "bun" that's sturdy, slightly sweet, and adds something real to the burger instead of just holding it. Top a grass-fed patty with smashed avocado and quick-pickled red onion, and you've got a burger that's messy in the best way and nutritionally miles ahead of the drive-through version. Our only warning: after this, a regular bun is firmly number two.

  • Prep25 minutes
  • Cook30 minutes
  • Total55 minutes
  • Servings4
  • PRO
  • GF
  • DF
  • PF
Estimated macros per serving

Calories ~600 · Protein ~34g · Carbs ~23g · Fat ~40g

Ingredients

For the pickled onion:
  • 1 medium red onion, thinly sliced into rings
  • ½ cup red wine vinegar
  • 1 tablespoon honey
  • ½ teaspoon fine sea salt
For the sweet potato buns:
  • 2 large sweet potatoes, cut into ½-inch-thick rounds (8 largest rounds)
  • 1 tablespoon extra-virgin olive oil
  • Kosher salt and freshly ground black pepper, to taste
For the burgers:
  • 1½ pounds grass-fed ground beef (85/15)
  • 1 teaspoon garlic powder
  • 1 teaspoon smoked paprika
  • Kosher salt and freshly ground black pepper, to taste
  • 2 ripe avocados
  • 1 tablespoon fresh lime juice
  • 4 leaves butter lettuce

Method

  1. Make the pickled onion first: Place the sliced red onion in a jar or bowl. Heat the red wine vinegar, honey, and ½ teaspoon salt in a small saucepan until just simmering. Pour over the onion, stir, and let sit at least 20 minutes. The longer they sit, the better they get. These will be quite tangy at 20 minutes; dilute with a splash of water if you prefer a milder pickle. Start the pickled onion first — the rest of the prep fills that time.
  2. Preheat the oven to 400°F (204°C). Line a baking sheet with parchment.
  3. Brush the sweet potato rounds with olive oil and season with salt and pepper. Roast for 12–15 minutes per side, until tender and lightly caramelized on the edges. You want them cooked through but sturdy enough to hold a burger.
  4. While the sweet potatoes roast, divide the ground beef into 4 equal portions. Season with garlic powder, smoked paprika, salt, and pepper. Form into patties about ¾ inch thick, slightly wider than your sweet potato rounds (they'll shrink). 85/15 is leaner — watch the temperature closely and pull the patties as soon as they hit 160°F to avoid drying out.
  5. Heat a cast-iron skillet or grill to high heat. Cook the patties for about 4 minutes per side, until they reach 160°F (71°C) internally — this is the USDA-recommended safe temperature for store-bought ground beef. Let rest 3 minutes.
  6. Mash the avocados with lime juice, salt, and pepper until chunky-smooth. Make the avocado mash just before serving — it does not keep well.
  7. Assemble: Place a sweet potato round on the plate, add a lettuce leaf, then the patty, a generous spoonful of smashed avocado, a tangle of pickled onion, and top with a second sweet potato round. Press gently and commit.

Variations & Notes

  • Vegan Swap: Use a thick portobello cap or a seasoned black bean patty in place of the beef, and brine the pickled onion with maple syrup instead of honey. The pickled onion and avocado carry a lot of the flavor.
  • Extra Hungry: Make double patties, or serve with a side of roasted Brussels sprouts or a simple green salad.
  • Substitutions: Turkey or bison also work beautifully here. If you want more heat, add a few slices of pickled jalapeño.
  • Storage: Cooked patties keep 3 days refrigerated. Sweet potato rounds keep 4 days. Pickled onions last up to 2 weeks in the fridge and only get better. Avocado mash: prepare fresh; does not keep well. Assemble fresh.