First, preheat the oven to 220°C (425°F). Position the oven rack in the center so the pork cooks evenly from all sides. Meanwhile, remove the pork tenderloin from the refrigerator and let it sit at room temperature for about 10 minutes. This short rest helps the meat cook more evenly and prevents a cold center.

Next, pat the pork tenderloin completely dry using paper towels. This step is essential because removing surface moisture helps the meat develop a golden crust during searing. Then, sprinkle the salt and pepper evenly over all sides of the tenderloin. Press gently so the seasoning adheres properly.

After that, prepare the garlic mustard paste. In a medium bowl, combine the brown sugar replacement, pressed garlic, 2 tablespoons avocado oil, Dijon mustard, apple cider vinegar, paprika, and chipotle powder if using. Stir thoroughly until the mixture forms a thick, slightly grainy paste. The texture should be spreadable but not runny. If it looks too dry, add a few drops of oil and stir again.

Meanwhile, heat the remaining 1 tablespoon avocado oil in an oven-safe skillet over medium heat. Allow the oil to heat until it shimmers lightly but does not smoke. Then, carefully place the pork tenderloin in the skillet. You should hear an immediate sizzling sound.

Next, sear the pork on all sides. Turn it every 45 to 60 seconds using tongs so that each side develops a golden brown crust. Continue until all surfaces are evenly browned, which usually takes about 3 to 4 minutes total. This step builds deep flavor and helps seal in juices.

After searing, remove the skillet briefly from heat. Then, using a spoon or spatula, spread the garlic mustard paste evenly over the entire surface of the pork tenderloin. Make sure to coat all sides generously. The paste will form a flavorful crust as it roasts.

Immediately transfer the skillet to the preheated oven. Roast the pork uncovered for 18 to 25 minutes. Begin checking the internal temperature after 18 minutes using a meat thermometer inserted into the thickest part. The target temperature is 60°C (140°F). At this stage, the pork will still be juicy and tender.

Once the desired temperature is reached, remove the skillet from the oven. Transfer the pork tenderloin to a cutting board. Then, let it rest for exactly 5 minutes. This resting period allows the juices to redistribute throughout the meat, ensuring maximum tenderness.

Finally, slice the pork tenderloin into medallions about 1 to 2 cm thick. Use a sharp knife and cut gently to preserve the juices. Serve immediately while warm.