Directions
If cooking with tenderloin: Pat steaks dry with paper towels and season with salt and pepper. Heat 1 tablespoon oil in large skillet over medium-high heat until just smoking. Cook steaks until well browned and meat registers 125 degrees for medium-rare, 3 to 5 minutes per side. Transfer to platter and tent with foil.
Add remaining tablespoon oil and shallots to empty skillet and cook until softened, about 2 minutes.
Stir in tomato paste and cook until beginning to brown, about 1 minute.
Stir in port, broth, and thyme and simmer, scraping up any browned bits with wooden spoon, until sauce is slightly thickened, about 5 minutes.
Off heat, whisk in vinegar, butter, and any accumulated steak juices. Season with salt and pepper. Pour sauce over steaks. Serve.