Preheat the oven to 350˚F.
Pat the beef dry with paper towel and season with salt. Heat an ovenproof skillet over medium-high heat, add a generous drizzle of oil and brown the roast on all sides.
Meanwhile, combine the garlic, thyme and pepper in a small bowl.
Turn off the heat and brush the meat all over with mustard; sprinkle with the spice mixture.
Scatter the tomatoes around the meat in the pan, and drizzle with a little more oil. Roast in the oven for 20 minutes, or until the internal temperature reads 145˚F.
As the meat rests (for 10 minutes), stir together the mayonnaise, blue cheese and cream, mashing the blue cheese into the mixture with a fork, and serve with the sliced beef and tomatoes.