Preheat oven to 425°. Line a rimmed baking sheet with foil; place a wire rack on top.
Place beef on rack. In a small bowl, stir together butter and garlic. Rub mixture all over beef, and sprinkle with salt and peppercorns.
Bake until a meat thermometer inserted in thickest portion registers 135° for medium-rare, 25 to 35 minutes, or desired doneness. Cover loosely with foil, and let stand for 15 minutes before slicing.
In a small bowl, stir together sour cream and horseradish; top with chives. Serve sauce with beef. Garnish with garlic and rosemary, if desired.
Recipe by Paula Deen Magazine at https://pauladeenmagazine.com/beef-tenderloin-with-horseradish-sauce-recipe/