Place roast in a large resealable plastic bag and set into a shallow dish. Pour Soy Sauce over the roast and close bag. Marinate in the refrigerate at least 8 hours or overnight; turning roast occasionally to distribute marinade.
On the morning of the day you want to served this roast: In a large heavy frying pan or cast-iron frying pan, melt butter and Worcestershire Sauce together. Add the roast (and remaining soy sauce) and brown on all sides. NOTE: This step gives color and flavor to the meat. Remove from heat and set aside.
About 45 minutes before serving time, preheat oven to 450 degrees F.
Place the browned roast in an open roasting pan or the cast-iron frying pan. Roast in the oven for approximately 45 minutes until medium-rare or until a meat thermometer registers an internal temperature you desire.
Rare - 120 degrees F.
Medium Rare - 125 degrees F.
Remove from oven and transfer onto a cutting board; cover with a tent of aluminum foil and let stand 15 minutes before carving (internal temperature will rise 5 to 10 degrees after it is removed from the oven).
While the roast is resting, make a sauce out of equal amounts of sour cream and horseradish. This can be made 1 day ahead of time. Refrigerate until ready to serve.
NOTE: I also make Knorr Bearnaise Sauce (according to direction on the package). Add 1 teaspoon dried tarragon and fresh-squeezed lemon juice from 1/2 of a fresh lemon. This can also be made 1 day ahead of time. Refrigerate until ready to serve.
To Serve: Cut the roast into approximately 1/2-inch slices (can slice thinner if desired). Transfer onto a serving platter and serve immediately with the Sour Cream/Horseradish Sauce and/or Bearnaise Sauce.
Beef Tenderloin Roast Recipe: https://whatscookingamerica.net/karencalanchini/beeffiletmignonroast.htm