8 flour tortillas (6 inch)
1 can (15 ounces) refried beans
2 tablespoons vegetable oil
1 large white onion, halved and cut into 1/2-inch slices
2 large poblano chiles, halved, seeded, and cut crosswise into 1/2-inch slices
2 medium zucchini, cut into 1/2-inch half-moons
2 cups corn (10 ounces), thawed if frozen
Coarse salt and ground pepper
1/2 cup salsa
1/2 cup sour cream
2 ounces cheddar or Colby, shredded (1/2 cup)
Lime wedges