1 pepper, plus 1 teaspoon sauce from a can of chipotle chile in adobo (see Tips)
1 clove garlic, minced
1/2 cup orange juice
3 tablespoons lime juice
1 tablespoon red-wine vinegar
1 teaspoon dried oregano
1/2 teaspoon ground cumin
1/4 teaspoon salt
1/4 teaspoon freshly ground pepper
8 ounces pork tenderloin, (see Tips), trimmed
1 small green bell pepper, cut into 1-inch-wide strips
1 small red bell pepper, cut into 1-inch-wide strips
1 small red onion, cut into 1/2-inch-thick rounds
2 teaspoons canola oil
4 6-inch or two 10-inch flour tortillas, preferably whole-wheat, warmed (see Tips)
1/4 cup nonfat sour cream
1/4 cup prepared salsa
Combine chipotle chile and sauce, garlic, orange juice, lime juice, vinegar, oregano, cumin, salt and pepper in a blender or mini food processor; blend or process until the chipotle is chopped and the mixture is relatively smooth. Pour into a sealable plastic bag, add pork and seal, squeezing out any excess air from the bag. Turn to coat with the marinade. Refrigerate at least 1 hour and up to 8 hours.
Preheat grill to high or heat a large indoor grill pan over high heat. Remove the pork from the marinade (discard marinade). Grill the pork, turning occasionally, until an instant-read thermometer inserted diagonally into the center of the meat registers 145°F, 12 to 15 minutes. Transfer the pork to a cutting board and let rest for 5 minutes before slicing.
Lightly brush bell peppers and onion with oil. Grill until lightly browned and soft, turning once, 3 to 7 minutes. (If using a grill pan, you may need to grill the vegetables in two batches.) Let cool on a cutting board.
Thinly slice the pork and chop the onion. Toss the onion, peppers and pork together.