Season: Take the rump steaks out of the refrigerator one hour before cooking. Pat them dry using kitchen paper. Rub with salt and pepper on both sides.
Heat the cast-iron skillet very well, about 4-5 minutes. Add the oil, turn the pan carefully to coat the bottom with the oil, then add the steaks. If using, add the cherry tomatoes as well. Turn the tomatoes often while they are in the pan.
Cook the steaks for about 2 minutes on the first side. Turn using tongs and continue cooking for another 2 minutes on the other side. The steaks will be medium-rare. If you want the steaks to be medium well or well done, add 1-2 minutes to the cooking time. See notes.
The best way to check if the steaks are done to your liking is to check the internal temperature using a meat thermometer. The cooking times always depend on the thickness of the steak, the pan you use, and the temperature of the pan, so only a thermometer and experience can guarantee the perfect results.
Rest: Remove the steaks from the pan, cover loosely with aluminum foil, and let rest for 5-10 minutes.
Tomatoes: During this time continue cooking the cherry tomatoes in the skillet for 2 or 3 more minutes or until slightly blistered and done to your liking; they should be soft but not turn mushy.
Slice the tagliata and serve as suggested above.