Preheat and prep. Heat the oven to 400°F (200°C).
Pat the pork dry with paper towels. Mix salt, pepper, garlic powder, and paprika. Rub the spice mix all over the tenderloins.
Make the glaze. In a small bowl, whisk peach preserves, Dijon, vinegar, soy sauce (if using), red pepper flakes, and thyme until smooth.
Sear the pork. Heat 1 tablespoon olive oil in a large oven-safe skillet over medium-high.
Add pork and sear until browned on all sides, about 2–3 minutes per side. Don’t rush this step—good color means better flavor.
Glaze and roast. Reduce heat to medium-low. Spoon about half the glaze over the pork and turn to coat.
Transfer the skillet to the oven and roast 12–16 minutes, until the thickest part reaches 140–145°F (60–63°C).
Rest and finish. Move the pork to a cutting board and let it rest 5–8 minutes. Meanwhile, place the skillet back on low heat on the stove. Add the remaining glaze with 1 tablespoon water and simmer 1–2 minutes until glossy.
Slice and serve. Slice pork into 1/2-inch medallions.
Spoon warm glaze over the top. Garnish with fresh peach slices and a squeeze of lemon if you like.
Serve with sides. Great with roasted potatoes, herbed rice, grilled corn, or a simple arugula salad.