Spicy Lentil-Walnut Burgers

In the bowl of a food processor, combine walnuts, breadcrumbs, garlic, jalapeno, cumin, coriander, red pepper flakes, 1 1/2 teaspoons salt, and 1/4 teaspoon pepper; process until finely ground. Add lentils, onion, and 1 tablespoon oil; pulse until coarsely chopped (some lentils should remain whole).

In a large bowl, whisk egg. Add lentil mixture; mix until well combined. Divide into quarters; roll into balls, and flatten with the palm of your hands into 3/4-inch-thick patties.

Heat remaining 3 tablespoons oil in a large nonstick skillet. Add burgers; cook, turning once, over medium-low heat until crisp and browned, 8 to 10 minutes per side. Transfer to a paper-towel-lined plate to drain. Serve burgers in pitas with sauce, avocado, and cherry tomatoes.