1 large sweet onion, cut crosswise into 4 thick slices
Extra-virgin olive oil, for brushing
Salt and freshly ground pepper
3 large navel oranges
2 tablespoons finely chopped cilantro
2 canned chipotle chiles in adobo, seeded and thinly sliced, plus 1 teaspoon
2 tablespoons fresh lime juice
1 tablespoon orange marmalade
Three 10- to 12-ounce pork tenderloins, each cut into 6 pieces and lightly
Light a grill. Carefully insert a skewer into each slice of onion to keep the rings from separating. Brush the slices with olive oil and season with salt and pepper. Grill over high heat, turning once, until charred on both sides, about 5 minutes. Remove the skewers and coarsely chop the onion.
Using a sharp knife, peel the oranges, carefully removing all of the bitter white pith. Halve the oranges lengthwise and thinly slice them crosswise. In a medium bowl, toss the grilled onion with the oranges, cilantro, chipotles and 1 tablespoon of the lime juice; season with salt and pepper. In a small microwave-safe bowl, mix the orange marmalade with the adobo sauce and the remaining 1 tablespoon of lime juice. Microwave the marmalade until melted, about 10 seconds.
Brush the pork with olive oil and season with salt and pepper. Grill over high heat, turning once, until just cooked through, about 6 minutes. Brush the marmalade over the pork and grill until lightly glazed, about 1 minute per side. Transfer the pork to plates and serve with the orange salad.