Step by step

Add the garlic, if you wish

Tips
If you like pungent flavours, add some anchovies to your gratin mixture
Trivia
The "San Marzano" name of the tomatoes used in this recipe is derived from the geographical region of Italy whence they come: San Marzano sul Sarno. Despite the fact that its name suggests a well-defined region of origin, it is a variety that grows well almost everywhere, if properly watered.