In a bowl, mix the Dijon mustard, olive oil, lemon zest, and lemon juice together. Place the beef in the marinade, cover with foil or plastic wrap, and refrigerate for at least 4 hours or overnight, turning the meat every 2-3 hours.
Preheat the oven to 100°C (212°F) with top/bottom heat. Heat olive oil in a large pan over medium-high heat until it shimmers. Sear the beef on all sides for 1-2 minutes per side until browned. Transfer to a baking dish and add the garlic cloves and rosemary stalks around the meat. Insert a meat thermometer into the thickest part of the meat.
Place the baking dish in the oven and reduce the oven temperature to 90°C (194°F) with top/bottom heat. Roast until the meat thermometer reaches 58°C (136°F), approximately 90-120 minutes depending on the thickness of the meat. Turn off the oven and leave the meat inside to rest for 5 minutes.
Remove the baking dish from the oven. Transfer the meat to a cutting board and slice. Serve with rosemary potatoes, vegetables such as green beans or Brussels sprouts, or a fresh salad.
For the sauce, mix meat broth concentrate with water and red wine to taste. Serve the beef with the sauce and a dry red wine.
The Boss Kitchen editorial staff oversees content review, fact-checking, and recipe verification across the site. Published articles pass through the editorial team before going live, ensuring ingredient lists, techniques, cooking times, and nutritional claims hold up in a home kitchen. The team coordinates contributions across the site writers, handles reader corrections, and maintains consistency in measurement conventions, safety guidance, and dietary labeling. Posts under this byline typically represent team-reviewed reference material, site announcements, or editorial roundups rather than individual-author features, and they are held to the same sourcing standards as bylined recipe and product coverage.