In a large pan, put olive oil.
Add onions, cover.
Next, allow the onions to lightly brown on medium-low heat.
Once the onions are slightly caramelized, add the can of tomatoes.
Again, cover and allow the mixture to cook covered for about 5 minutes to combine.
Then, add tomato paste and water.
Combine via stirring.
Cover and simmer for 30 minutes.
Remove from heat and remove the lid from pan.
Allow the sauce to thicken.
Use atop fettuccine, beans, Sicilian Pizza, etc.