Preheat your oven to 425°F.

Prepare the stuffing by mixing together breadcrumbs, minced garlic, chopped onion, softened butter, and parsley in a bowl until well combined.

Slice the beef tenderloin lengthwise, opening it up like a pinwheel.

Spread the stuffing mixture generously over the flattened tenderloin.

Roll the beef up tightly, securing it with butcher's twine every inch.

Season the outside of the tenderloin with salt and pepper.

Place the tenderloin in a roasting pan on a wire rack.

Roast in the oven for 50-70 minutes, checking it reaches an internal temperature of 145°F for medium-rare.

Let rest for 15-20 minutes before slicing.

Optional: Drizzle with a balsamic reduction for an elegant finish.