Preheat and prep: Heat your oven to 425°F (220°C). Pat the pork dry with paper towels.
Dry meat sears better and develops a flavorful crust.
Season the vegetables: In a large bowl, toss potatoes, carrots, red onion, and bell pepper with 2 tbsp olive oil, half the salt and pepper, and half the paprika and thyme. Spread them in a single layer on a large oven-safe skillet or sheet pan.
Start roasting the veggies: Roast the vegetables for 12 minutes. This head start ensures the potatoes and carrots get tender by the time the pork is done.
Make the pork rub: In a small bowl, combine the remaining salt, pepper, paprika, thyme, garlic powder, onion powder, Dijon, honey, lemon juice, 1 tbsp olive oil, and the minced garlic.
Stir into a thick paste.
Season and sear the pork: Rub the paste all over the pork tenderloin. Heat a large oven-safe skillet over medium-high. Sear the pork 1–2 minutes per side until browned.
If you used a sheet pan for the veggies, you can sear in a separate skillet.
Combine and roast: Pull the vegetables from the oven. Nestle the seared pork on top of or alongside the vegetables. Return the pan to the oven and roast 12–18 minutes, depending on thickness.
Check doneness: Use an instant-read thermometer.
Pull the pork at 140–145°F (60–63°C). It will rise a few degrees as it rests.
Rest and finish: Transfer the pork to a cutting board and rest 5–8 minutes. Toss the vegetables in the pan drippings.
If you like a brighter finish, splash with a little extra lemon juice or vinegar.
Slice and serve: Slice the pork into 1/2-inch medallions. Serve over the roasted vegetables and garnish with chopped parsley. Spoon any juices from the board and pan over the top.