1. Fill a pot for the pasta with about 6 quarts of water, place over high heat, and bring to a boil.

2. Peel the onion and finely chop it. Put it and the olive oil in a 12-inch skillet and place over medium-high heat. Sauté until the onion turns a rich golden color, about 5 minutes.

3. While the onion is sautéing, peel the garlic and finely chop it. Finely chop enough rosemary to measure 1 teaspoon. Peel the tomatoes and coarsely chop them.

4. When the onion is ready, add the garlic and rosemary. Sauté for 10 to 15 seconds, then add the tomatoes. Season lightly with salt and cook until most of the liquid the tomatoes release has evaporated, about 10 minutes. Add the chickpeas, season with pepper and again lightly with salt, and cook for 5 more minutes. Scoop out about half the chickpeas and puree them. A food mill will produce a smoother texture, but if you don't have one you can use a food processor. Mix the pureed chickpeas into the sauce and cook for another 1 to 2 minutes.

5. Once the pureed chickpeas are back in the pan, add about 2 tablespoons salt to the boiling pasta water, add the tagliatelle, and stir until all the strands are submerged. Cook until al dente.

6. After the pasta has cooked about 2 minutes, mix 2 tablespoons of the pasta water into the sauce. When the pasta is done, drain well and toss with the sauce. Drizzle a little olive oil and grind some black pepper over each portion and serve at once.