First prepare the beef: lay the slice of meat out on your work surface, season it with 2 spoonfuls of olive oil and some salt, then cover it with the slices of pancetta. Sprinkle with the breadcrumbs mixed with finely chopped parsley and garlic. Then add the tomato – cleaned, washed and cut into small pieces – and, finally, the pecorino cheese in slivers. Roll up the meat and truss it with cooking string; tuck the bay leaves under the string, season with salt and pepper, and transfer into a roasting pan. Drizzle with the remaining 2 spoonfuls of oil and cook in a preheated oven, at 180 °C, for an hour; Check the meat from time to time and, when it has browned on one side, turn it over and baste it with the juices in the pan. For the vegetables: clean and finely chop the onion, then sauté it in a heavy-bottomed frying pan with the olive oil over a low heat. Clean and wash the pepper, pat it dry, cut it in half and remove the seeds and internal membranes. Cut it into thin strips and add to the pan with the sautéed onions, season with salt and cook for a few minutes over a very low heat. Mix the vinegar with the sugar and pour it over the vegetables, stir and cook for about 10 minutes. Should the peppers become too “dry”, add a little warm water. After 45 minutes in the oven, take the meat out and add the peppers to the roasting tin; then put it back in the oven for the last quarter of an hour. When this time has passed, take the tin out of the oven again and leave the meat to “rest” for 15 minutes. Then transfer it onto a chopping board, remove the string and cut the beef into slices; arrange them on a serving dish with the peppers and serve.