1large red or yellow onionpeeled and cut into 1 1/2-inch chunks
1large fennel bulbtrimmed and cut into 1 1/2-inch chunks
10small white or red potatoeshalved or cut into quarters, whatever gets you to 1-inch or so pieces
2jalapeno peppershalved lengthwise, seeded, and sliced
Preheat the oven to 425°F.
In a small bowl, mix together the coriander, thyme, garlic, 1 teaspoon salt and 1/2 teaspoon pepper. Rub the mixture over the pork loins. Heat a large cast heavy skillet over high heat. Add 2 tablespoons of the oil, then add the pork loins and sear on all sides until lightly browned, about 6 minutes in all.
Meanwhile, on a rimmed baking sheet, gently toss the onions, fennel, potatoes and jalapenos with the remaining 2 tablespoons olive oil and salt and pepper to taste. Tuck the thyme leaves amongst the vegetables.
Nestle the four pork loins pieces amidst the vegetables.
Roast for 30 minutes, until the pork reaches an internal temperature of 140°F. Remove the pork loins and let them sit on a cutting board, lightly tented with foil, spread out the vegetables evenly on the baking sheet, and roast them for another 10 minutes or so, until they are golden brown and tender.
Slice the pork loin and serve the with roasted vegetables.