The four Roman pasta sauces

Roman pasta rests on two ingredients: pecorino romano, the sharp sheep's cheese, and guanciale, the cured pork jowl. From that small pantry the city built four canonical sauces, and the easiest way to understand them is to watch what gets added at each step.

Cacio e pepe

The base. Pecorino and black pepper, loosened with starchy pasta water into a glossy emulsion. No fat but the cheese, no meat at all. It wants a shape with grip and a rough surface so the cheese clings rather than clumps, which is why Rome serves it on tonnarelli, the square-cut egg strand, or on a sturdy spaghetti.

Gricia

Add guanciale. Gricia is cacio e pepe with the rendered pork folded in, sometimes called amatriciana bianca, the white amatriciana, because it is the same dish without the tomato. Rigatoni and mezze maniche, ridged tubes, hold the fat and cheese in their grooves.

Amatriciana

Add tomato. Guanciale, pecorino, and a tomato sauce, named for the town of Amatrice. Bucatini is the classic carrier, its pierced center pulling the sauce inside, though rigatoni is just as at home.

Carbonara

Add egg instead of tomato. Guanciale, pecorino, and raw egg yolk cooked only by the heat of the pasta into a silky coat, with lots of black pepper. No cream, despite what the rest of the world does to it. Spaghetti and rigatoni both work; the sauce needs a shape sturdy enough to toss hard off the heat.