Make seasoning: In a food processor blend half of the onion, a quarter of the bellpepper, oregano, garlic, a pinch of pepper, and a teaspoon of salt.
Stuffing the meat: Cut the meat into a tube by inserting the knife lengthwise (in the same direction of the fibers). Season the meat inside and out with the blended mix. Stuff the beef with the longaniza, some onion strips, some bell pepper strips, and some carrot strips. Wrap with twine (if you have), to keep the roll more compact, juicier and beautiful. Marinate covered in the refrigerator for at least an hour.
Brown the meat: After the hour has passed, heat the oil in a large heavy-bottomed pot (6 qt [6 lt] over high heat. Remove the meat from the marinade, reserve the marinade for later use. Pat dry the meat with a paper towel. Place the meat in the heated oil, carefully to avoid burning yourself. Brown the meat, turning every few minutes to get a uniform brown color all over.
Make the sauce: While the meat browns, mix a cup of water, tomato sauce, flour, and the remaining marinade. Remove the meat from the pot and discard the twine. Meanwhile pour the tomato sauce mixture into the pot, stirring to incorporate all the browned bits. Stir in the olives, capers, and the remaining carrot, bell peppers, and onion. Place the meat back into the pot.
Cook the roll: Lower the heat to a minimum, cover with a tight-fitting lid and simmer for 30 minutes, rotating the meat every so often so it cooks uniformly. The sauce should have been reduced to half, if it is too dry, add additional water.
Serving: Once this time has passed, remove the meat from the sauce, place it on a cutting board, and cut it into slices.Season the sauce with salt and pepper to taste. Pour the sauce into a serving plate and place the slices on top. Sprinkle with parsley.Serve per suggestions above the recipe.
Notes
I have made some minor changes to the traditional Carne Mechada, changes that after much experimentation I have found improve the recipe considerably. I hope you like them as much as I did.