1. Make the burgers: In a medium saucepan, add the lentils, sweet potato and water and bring to a boil over medium-high heat. Reduce the heat to medium-low and gently simmer until the lentils and potatoes are tender, about 25 minutes. Drain the mixture through a fine-mesh sieve and transfer the lentil mixture to a food processor.

2. To the lentil mixture, add the onion, egg, panko breadcrumbs, sesame seeds, cumin, marjoram, oregano, sumac (if using), salt and pepper. Pulse until coarsely chopped, about five 1-second pulses. Shape the mixture into four 4- to 4½-inch patties, each about ½ inch thick.

3. Heat a large nonstick skillet over medium heat. Lightly coat the skillet with nonstick pan spray and add two of the lentil burgers. Cook until the burgers are browned, 3 to 4 minutes, then flip and cook on the other side, about 3 minutes more. Transfer to a large plate and repeat with the remaining patties.

4. Make the sauce: To a medium bowl, add the feta cheese, then use a fork to crumble it. Stir in the yogurt and mint.

5. Slice open each pita to create 2 round slices. Place a lentil burger on 4 bottom rounds and top each with some of the feta sauce and a few tomato slices. Top with the remaining pita rounds. Serve immediately. Calories per Serving: 340; Sodium: 1030mg; Total Carbohydrate: 54g; Fiber: 8g; Fat: 6g