These spicy burgers are bound together with masa harina, the corn flour used to make corn tortillas and tamales. Cornmeal works just as well, though the burger texture will have more of a crunch. Serve on a warmed tortilla with avocado, if desired.
1. Bring rice and 3 cups water to a boil in medium saucepan. Reduce heat to low, cover, and simmer 40 minutes, or until water is absorbed, and rice is tender.
2. Meanwhile, heat oil in large skillet over medium heat. Add onion, bell pepper, corn, chipotle, adobo sauce, garlic, cumin, and salt. Sauté 2 minutes, then reduce heat to low. Cover, and cook 15 minutes, or until vegetables are tender, stirring once or twice. Whisk 1/2 cup water with masa harina in bowl. Add to skillet mixture, cover, and cook on low 10 minutes more, stirring once or twice (mixture will feel like thick cornmeal mush).
3. Remove from heat, and stir in hot rice, cilantro, lime juice, and zest. Cool 20 minutes. Wet hands and shape mixture into 8 burgers. Refrigerate 30 minutes.
4. Prepare charcoal fire or gas grill for medium heat. Brush burgers and grill rack with olive oil. Grill 7 minutes per side, or until crusty on the outside. If adding cheese, top burgers during the last 3 minutes of grilling.