1 large white onion, halved
1 pineapple, peeled, cut crosswise into 1/2-inch-thick rounds
1/2 Cup fresh orange juice
1/4 Cup Traditional White Balsamic Vinegar
1/4 cup Guajillo Chile Powder
3 garlic cloves, halved
2 tsp Coarse Kosher Salt
1 tsp Dried Mexican Oregano
1 tsp Ground Cumin
1 large or 2 small chipotle chiles and 1 to 2 teaspoons adobo from canned chipotle chiles in adobo
1 2 1/2-to 3-pound boneless pork loin, cut into 1/2-inch slices
1/4 cup chopped fresh cilantro
Coarsely chop 1 onion half. Coarsely chop 2 pineapple rounds, discarding core; cover and chill remaining pineapple. Place chopped onion and chopped pineapple in blender. Add orange juice and next 7 ingredients; puree marinade until smooth. Place pork in large resealable plastic bag. Add marinade and seal bag, releasing excess air. Turn to coat. Chill at least 4 hours and up to 1 day.
Prepare barbecue (medium-high heat). Grill remaining pineapple until warm and slightly charred, 4 to 6 minutes per side. Grill pork with some marinade still clinging until slightly charred and cooked through, 2 to 4 minutes per side. Transfer pineapple and pork to work surface; chop pineapple into 1/2-inch cubes, discarding cores. Chop pork. Transfer to platter; toss to combine.
Meanwhile, finely chop remaining onion half and place in medium bowl. Add cilantro; toss to combine. Grill tortillas until warm and slightly charred, about 10 seconds per side.
Serve pork-pineapple mixture with onion-cilantro relish, Smoky Two-Chile Salsa, and lime wedges.