In a blender
or food processor
, puree the tomatoes to a smooth, creamy consistency.
Add the olive oil to a large pan over medium heat. Once hot, add the anchovies and onions
and saute until the onions are soft and the anchovies have melted into the onions. Toss in the capers and garlic, and if you'd like to make the sauce
spicier, add a pinch of red pepper flakes. Saute until the garlic is fragrant.
Add the tomatoes
and season with salt and pepper. Bring to a simmer and simmer
on a medium-low flame for about 30 minutes. Strive for balance in the consistency of the sauce; it has to be fluid but it should not look overly wet. A few minutes before taking the sauce off the fire, add half the basil
and more salt and pepper if needed. Garnish
with the remaining basil just before serving.