Tonnarelli is the Roman name for the pasta you may know by its more popular Abruzzese name, spaghetti alla chitarra. It is a fresh pasta that looks like square spaghetti. In Rome, this pasta is sold in any supermarket but elsewhere, you may find you have to make it yourself. Due to its thickness (and the optional use of semolina flour), homemade tonnarelli provides quite a bit more ‘bite’ than your average fresh pasta. And that’s good thing for robust Abruzzese sauces or the typical Roman treatment, cacio e pepe.
To make tonnarelli, you need a special instrument called a chitarra, or guitar, which is why tonnarelli are also called spaghetti alla chitarra. Here’s a picture of a pasta ‘guitar':
The guitar is fitted with wire ‘string’s top and bottom that are used to cut the pasta. The strings are narrowly spaced on one side, and widely spaced on the other. For tonnarelli, you want to use the side with the narrowly spaced strings. To begin, make some fresh pasta dough in the usual way—adding just a tablespoon or two of semolina flour per egg if you like for extra ‘bite’—and roll it out quite thick. The pasta should be as thick as it is wide, so you can be guided by the strings of your ‘guitar’. (Using a KitchenAid mixer attachment, use Setting 1 or 2.) Let the pasta sheets dry out for a good while (at least 20 minutes) so they will not stick too much as they are cut by the guitar. Cut your pasta into sheets about as long as the chitarra, leaving some room on each end for the pasta to stretch out, which it will as you proceed.
Then, with a rolling pin, begin to flatten the pasta against the strings:
Very soon, the pasta will have passed between the strings, but will still cling to them, so that they will show flush with the pasta like this:
Now it’s time to ‘play’ your guitar. Run your fingers along the length of the strings until the pasta begins to detach from the strings. Continue playing your guitar until the pasta has detached completely and fallen into the tray below:
Slide the tonnarelli out of the chitarra and lay them out to dry on a wooden board or towel. Repeat the operation with each additional pasta sheet. (NB: Depending on how dry the pasta sheets are, you may need to separately some of the strands by hand.) Due to its thickness, homemade tonnarelli take a bit longer to cook than other kinds of fresh pasta, as long as 5 minutes or more depending on how long it has been drying.
Homemade tonnarelli are sometimes made exclusively with hard durum wheat flour (semolina) and sometimes just with “00” flour, which changes the character of the pasta considerably. I prefer neither ‘extreme’ and use mostly “00” (or simply all-purpose) flour with just a spoonful of semolina.
Besides their use in the Roman classic cacio e pepe, in the cooking of Abruzzo, spaghetti alla chitarra (as tonnarelli are called there) are typically dressed with a lamb-based ragù. Tonnarelli are also very good with shellfish sauces. Indeed, they are extremely versatile and lend themselves to all sorts of sauces and condiments. De Cecco makes a dry pasta version of spaghetti alla chitarra, which is available through amazon.com. I have not tried it, but I have to imagine that the dry version, while surely good, will not give the same results as the fresh homemade tonnarelli.