Step 1

1. Preheat oven to 350° F.
2. In a small baking dish, toss the garlic cloves and olive oil to coat the cloves thoroughly. Cover the baking dish and bake cover until the garlic cloves just begin to brown, about 35 minutes.
3. Drain olive oil and garlic into a food processor and let it cool for at least 15 minutes.
4. Add the fresh lemon juice, prepared horseradish, and ½ teaspoon kosher salt. Puree all the ingredients until they are almost smooth. Set aside.
5. Place a rack on large, rimmed baking sheet. Sprinkle the beef with the remaining ½ teaspoon salt and pepper.
6. Spread a thin layer of garlic mixture on underside of beef. Place the beef onto a rack with the garlic mixture-coated side down onto rack.
7. Spread the top and sides of the beef with remaining garlic mixture.
8. Cover with foil and refrigerate for at least 3 hours or up to 1 day.

Step 2

1. Preheat to 350° F.
2. Position the oven rack in bottom third of oven.
3. Uncover the beef, place it in the oven, and roast the meat until a thermometer inserted into the top center of the roast registers 125 degrees for rare. This will take about 1 hour 45 minutes, but check the temperature frequently after one hour to insure that the roast doesn’t overcook. Those last few degrees shoot up very quickly!
4. Transfer the beef to platter and let it stand 30 minutes.
5. Scrape pan juices into small saucepan so that you can reheat them when you serve the beef.
6. Slice beef across the grain. (An electric carving knife is very helpful if you have one.)
7. Re-warm the pan juices and drizzle them over the sliced beef.