Memorial Day is finally here and what’s better than a good burger in the summertime? The grass-fed beef in this super-tasty, high-protein recipe from barre3 delivers a healthy dose of iron, B12, zinc, and selenium—plus fiber, thanks to the leafy-green lettuce wrap. These are sure to be a hit at your next summer BBQ!

Ingredients:

1 tablespoon olive oil
½ teaspoon kosher salt, divided
1 large yellow onion, very thinly sliced
1 pound crimini mushrooms, stems removed, and thinly sliced
1 tablespoon reduced-sodium gluten-free tamari
1 teaspoon fresh, chopped rosemary
1 pound 10% grass-fed ground beef
8 Bibb lettuce or romaine leaves
2 sliced Roma tomatoes (for serving)
1/2 red onion, thinly sliced (for serving)

Instructions:

1. In a large pot or Dutch oven, heat the olive oil over medium heat. Add the onions and ⅛ teaspoon salt, stirring to combine. Partially cover and cook, stirring occasionally for 5 minutes, until the onions begin to wilt.
    
2. Remove the lid, and add the mushrooms and an additional ⅛ teaspoon salt, stirring to combine. Cook over medium-high heat for an additional 10 minutes, stirring occasionally, until the mushrooms have released their liquid and the pan is nearly dry.
    
3. Turn off the heat, and add in the tamari and rosemary, stirring to combine. Set aside.
    
4. Meanwhile, make the burgers by forming the beef into 4 patties. Sprinkle both sides with ¼ teaspoon salt.
    
5. Heat an outdoor grill, indoor grill pan, or cast iron skillet to medium heat. Grill the burgers for 3 minutes, then flip and cook an additional 4-5 minutes, until they’re golden and cooked to your desired doneness.
    
6. Serve the burgers wrapped in two lettuce leaves and topped with caramelized onions and mushrooms, sliced tomatoes, and red onions.

Note: Store any leftover caramelized onions and mushrooms for a later use, such as stirred into scrambled eggs, on top of salads, or in quinoa bowls.