Boil water and add some salt. Cook the pasta based on package instructions. Separate the pasta from the pasta water. Set aside.
Heat a pan. Add bacon and cook until crispy. Remove the bacon and set aside. Also remove half of the bacon fat and keep it for later use while leaving the other half on the pan.
Combine butter and bacon fat on the pan. Heat the pan and let the butter melt.
Once the butter and bacon fat mixture get hot enough, sauté onion and garlic until the onion softens.
Add the tuna. Cook for 1 minute.
Combine Knorr cream of mushroom with 1 ½ cup water. Mix well. Pour the mixture into the pot and let it boil.
Add bell pepper, half of the parsley, and half of the Parmesan cheese. Stir.
Add the fettuccine. Arrange until well blended. Note: add pasta water to make the sauce thinner, if needed.
Arrange the tuna carbonara on a pasta bowl and top with crispy bacon, parsley, and Parmesan.
Serve. Share and enjoy!