In a large pot, heat water (high heat). Once it starts boiling, add the cannelloni sheets (introducing them one by one so they don’t stick to each other). Boil them as directed in the package (mine was 15 minutes). Once they are ready, drain them and reserve for later.
In a pan add olive oil, the onion (peeled and chopped very finely), the green pepper (chopped very finely), and the carrot (peeled and chopped very finely). Sauté them (high heat) until they are soft.
Once the vegetables are ready, add the ground beef, a little bit of salt, and a little bit of pepper. Then mix all the ingredients and cook on high heat until the ground beef is fully cooked.
Once the beef is ready, add ½ cup of Spanish tomato sauce. Mix it very well with the rest of the ingredients and cook it for about 30 seconds.
Now take one of the cannelloni sheets, add some of the cooked meat in the center, and roll it. Then put it inside an oven proof container and repeat the process with the rest of the cannelloni sheets.
Once all of them are in the container, cover them with the béchamel sauce. Sprinkle some shredded parmesan cheese over it and put the butter in small pieces.
Bake it at 365°F (180°C) for 25 minutes or until golden.