Preheat oven to 450 degrees F. Whisk flour, 1/2 teaspoon salt and pepper in a shallow dish. Dredge turkey in the mixture. (Discard any leftover flour.)

Heat oil in a large ovenproof skillet over high heat. Add the turkey; cook until golden brown on one side, 3 to 5 minutes. Turn the turkey over and transfer the pan to the oven. Roast until the turkey is just cooked through and no longer pink in the middle, 15 to 20 minutes. Transfer the turkey to a plate and tent with foil to keep warm.

Place the skillet over medium heat. (Take care, the handle will still be very hot.) Add shallots and thyme and cook, stirring constantly, until the shallots begin to brown, 30 seconds to 1 minute. Add blueberries, vinegar and the remaining 1/4 teaspoon salt; continue cooking, stirring occasionally and scraping up any brown bits, until the blueberries burst and release their juices and the mixture becomes thick and syrupy, 4 to 5 minutes. Slice the turkey and serve with the blueberry pan sauce.

Ingredient Note: A turkey tenderloin is an all-white piece that comes from the rib side of the breast. Tenderloins typically weigh between 7 and 14 ounces each and can be found with other turkey products in the meat section of most supermarkets.