Italian tomatoes, preferably San Marzano or Romanello
Electric or manual tomato press (a.k.a. tomato mill)
Buy the tomatoes two or three days ahead of time and store them outdoors on a sheet to maximize their ripeness and develop their flavours.
Using a manual tomato press
Blanch the tomatoes by plunging them into boiling water for 2 or 3 minutes, depending on ripeness. Once removed from the water, slice them in half to check for rot. Discard any damaged tomatoes. Run the tomatoes through the press. Purée comes out one side, seeds and skins the other. The purée is ready for cooking.
Using an electric press
No blanching required—just wash the tomatoes and feed them into the machine. The purée is ready for cooking.
In several heavy-bottomed saucepans over medium heat, simmer the purée uncovered, stirring and skimming occasionally, until thick. Cooking will take 1 1/2 to 2 1/2 hours depending on the quantity of tomatoes and the size of the pots.