A simple garlic-and-tomato marinara built for dipping. Good canned tomatoes do most of the work — the rest is patience.
Sauté the sliced garlic and red pepper flakes in the olive oil until fragrant — don't let the garlic brown.
Add the fresh Roma tomatoes first, then the crushed canned tomatoes, along with the oregano, salt, and pepper.
Let it simmer down until it thickens to where you want it.
Stir in the fresh basil and the optional butter. Add the sugar only if the tomatoes taste sharp — good San Marzanos usually won't need it.
Look for Cento San Marzano style whole peeled tomatoes. Avoid anything labeled “Italian Style” — that's a marketing phrase, not an origin, and it's usually a lesser tomato.