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Air Fryer Keto Portobello Burgers

Portobello caps pre-cooked to shed water, then used as buns for a smashed beef patty with crisp edges — a bunless, low-carb burger.
Print Recipe
Prep Time 15 minutes
Cook Time 16 minutes
Total Time 31 minutes
Servings: 2 burgers
Course: Main Course
Cuisine: American
Calories: 480
Ingredients Equipment Method Notes

Ingredients
  

For the caps
  • 4 large portobello caps stems and gills removed
  • 1 tbsp olive oil
  • kosher salt
For the patties
  • 1 lb ground beef 80/20
  • kosher salt and black pepper
  • 2 slices cheese cheddar, provolone, or Swiss
To build
  • shredded lettuce, thin red onion, pickles
  • burger sauce 2 tbsp mayo, 1 tsp Dijon, 1/2 tsp smoked paprika

Equipment

  • Air fryer
  • Meat thermometer
  • Paper towels

Method
 

  1. Salt the gill sides 10 minutes, then pat dry. Brush the outsides with oil, leaving the gill sides mostly dry. Air fry gill-side down at 400°F for 6 minutes, flip, and cook 3 to 5 minutes more until the edges brown. Drain any pooled liquid.
  2. Form 4 patties slightly wider than the caps, 1/2 inch thick, with a shallow dimple in the centre. Season.
  3. Air fry at 400°F for 7 to 9 minutes, flipping at 5, to 135 to 140°F for medium. Add cheese in the last minute. Rest 3 minutes.
  4. Sandwich each patty between two caps with lettuce, onion, pickles, and burger sauce.

Notes

Pre-cook and drain the caps or the burger ends up soggy.
The dimple in the patty keeps it flat instead of doming.
Two caps per burger — top and bottom.