Heat a cast iron skillet over high heat. Liberally season all sides of the beef with salt and pepper.
Add olive oil and sear meat on all sides until browned. Add water and beef broth. Next, add garlic and herbs.
Place in oven and roast until internal temp is 115 degrees, about 12 - 15 minutes per pound.
Remove from oven to a cutting board and cover loosely with foil. Rest for 20 minutes. Temp will rise and should reach 130 degrees when ready to serve for medium rare. Thinly slice against the grain.
Strain remaining juices. Scoop out a little of the broth and mix with cornstarch. Dump back in to allow to thicken. Taste and adjust seasoning.
Cut baguette in half lengthwise. Brush mayo on bread if using. Generously pile on thinly sliced beef. If using cheese, top with provolone and return to the oven on broil. Carefully watch until cheese is melted.
Place other side of baguette on top. Cut into pieces and to serve, dunk sandwich into the broth.