For a veggie burger, place these in toasted buns. Top with sauteed onion, cheese, and arugula.
Preheat oven to 450 degrees. Place trimmed mushrooms, stem side up, on a rimmed baking sheet. In a bowl, combine the extra-virgin olive oil and fresh lemon juice. Pour over mushrooms and top with garlic slices, and rosemary. Season with coarse salt and ground pepper. Roast until tender, 10 to 15 minutes.