As you venture into the world of authentic Neapolitan style pizzas, you will learn that simplicity is at the heart of that style. By and large, the toppings for Neapolitan style pizzas are few and sparing in their application. Sauces tend to be very simple also--typically San Marzano tomatoes that are minimally processed. When they are used raw on pizzas that are baked in wood fired ovens at high temperature, those high temperatures will cook the tomatoes within a minute or two. I have seen recipes for more complicated sauces for Neapolitan pizzas, including in cookbooks devoted to Neapolitan pizzas, but they look to me suspiciously like what we would call "spaghetti sauce"--more like marinara sauces. If you'd like, I can give you an example or two of such sauces.
In addition to using the San Marzano tomatoes as mentioned above, the Neapolitan pizzaioli also use several types of cherry tomatoes, called pomodorini and piennolo. They are sweet tomatoes about an inch in diameter and are generally used uncooked (cut into thin slices or quartered) on pizzas. A local small tomato, called pendula, is also used on pizzas inasmuch as they can be used fresh and dried (they are often picked when still slightly green or yellow and hung in grapelike bunches from the rafters or balconies to mature, then quartered, salted and strewed with herbs before using on pizzas). As might be expected, these tomatoes are unlikely to be found fresh in the U.S., but there are a few Internet sources for imported canned Italian cherry tomatoes. The San Marzano tomatoes are now widely available in the U.S., but if you decide to use them you should search this site before buying since there are many different brands and they vary in quality, as fellow member scott has pointed out in earlier posts. You should also investigate those San Marzano tomatoes that carry the D.O.P certification (Denominazione di Origine Protetta, or denomination of protected origin) as being authentic San Marzano tomatoes (the varietal), which tend generally to be of higher quality (although not always) than those that do not carry that designation.
To give you an idea of the simplicity of Neapolitan style pizzas, I have cut and pasted below the pizza section of a menu of La Pizza Fresca Ristorante, a NYC restaurant that specializes in authentic Neapolitan style pizzas. This is an example only and is not intended to convey absolute authenticity. You will note, for example, that most of the La Fresca pizzas call for buffalo mozzarella cheese (bufala di mozzarella). But even in Naples you are more likely to see cow's milk mozzarella cheese (fior di latte) on pizzas. Buffalo mozzarella cheeses tend to have a lot of water in it, which may require draining before using, and it is also more expensive than cow's milk mozzarella cheese and generally reserved for use as an eating cheese. In restaurants in Naples, one generally has to ask for the buffalo mozzarella cheese version to be sure to get it. Also, seed oils are also commonly used in Naples instead of olive oil, as indicated in the LaFresca pizza menu.
Here is the La Fresca pizza menu, including the introduction to the list of pizzas:
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Our authentic pizza is crafted in the tradition of Napoli, Italia, the birthplace of pizza. We adhere to the standards set forth by the Associazione Vera Pizza Napoletana, using fresh ingredients. We use fresh imported Italian bufala mozzarella, our sauce is created with Italian San Marzano tomatoes, and our freshly prepared hand-pressed dough creates the authentic thin crust that made Neapolitan pizza famous.
Tomato sauce, extra virgin olive oil and garlic.
Tomato sauce, fresh bufala mozzarella, Parmigiano Reggiano, and olive oil.
“La Pizza Fresca” $13
Tomato sauce, fresh bufala mozzarella, Italian cherry tomatoes, black olives, Parmigiano Reggiano, and basil.
Salame Piccante $14
Tomato sauce, fresh bufala mozzarella, spicy pepperoni and black olives.
Quattro Stagioni $17
Prosciutto, mushrooms, fresh bufala mozzarella, tomato sauce and artichoke hearts.
Quattro Formaggi $14
Fresh bufala mozzarella, Gorgonzola, Fontina and Parmigiano cheeses.
Grilled eggplant, zucchini, roasted peppers and portobello mushrooms
with fresh bufala mozzarella and tomato sauce.
Sauteed pancetta (Italian bacon), onions and fresh bufala mozzarella.
Tomato sauce and balsamic vinegar topped with shaved Parmigiano cheese.
Sauteed mushrooms with fresh bufala mozzarella and tomato sauce.
Prosciutto di Parma $16
Tomato sauce and fresh bufala mozzarella topped with thinly sliced Prosciutto di Parma.
Anchovies, fresh bufala mozzarella, tomato sauce and fresh oregano.
Cime di Rapa $15
Broccoli rabe, sausage, and fresh bufala mozzarella.
Anchovies, capers, black olives, tomato sauce, garlic and fresh oregano.
Tomato sauce, sausage, sauteed mushrooms with extra virgin olive oil and garlic.
Focaccia alla Nevi $17
Lightly toasted pizza bread with an inner layer of tangy Robiola cheese
topped with fresh arugula, thinly sliced Prosciutto di Parma.