Preheat oven to 350°F (180°C). Heat oil in a skillet over medium-high heat. Add onion and red pepper and cook, stirring, until vegetables soften, approx. 5 min. Add beans, salt, pepper, spices and 1/4 cup (60 mL) water. Simmer for 5 min. more, stirring until beans soften slightly. Add lime zest, juice and cilantro.
Meanwhile, wrap tortillas in foil and heat in the oven for 5 to 10 min. Divide filling, cheese, avocado and lettuce evenly among the warm tortillas; top with sour cream and salsa, and serve.