Prep the Loin. Preheat your oven to 375°F (190°C). Rub the loin with olive oil, salt, pepper, garlic powder, and thyme.
Sear for flavor. Heat a skillet over medium-high heat. Sear the meat on all sides until golden brown—this locks in juices and flavor.
Make the blueberry sauce. In a small saucepan, combine blueberries, honey, balsamic vinegar, and red pepper flakes (if using). Cook over medium heat, stirring occasionally, until blueberries burst and the sauce thickens slightly (5–7 minutes).
Roast the Loin . Place the seared loin in a baking dish and roast in the oven for 25–30 minutes, or until internal temperature reaches 145°F (63°C).
Rest & serve. Let the loin rest for 5–10 minutes before slicing. Spoon the sweet blueberry sauce generously over the slices and serve immediately.