Rigatoni with Eggplant, Tomato, and Ricotta

Fill a 5-quart kettle three fourths full with salted water and bring to a boil for pasta. Chop onion and cut eggplant into 1-inch cubes. Mince garlic. In a large deep heavy skillet heat oil over moderately high heat until hot but not smoking and sauté onion, stirring occasionally, until softened. Add eggplant and salt and sauté, stirring frequently, until eggplant is lightly browned. Add 1/2 cup water to eggplant mixture and cook, covered, over moderate heat, stirring occasionally, adding more water, 1/4 cup at a time, if mixture becomes dry, until eggplant is tender, about 10 minutes. Add tomatoes with juice and simmer, stirring vigorously to break up tomatoes, 5 minutes, or until mixture has a sauce-like consistency. Stir in garlic and basil and season with salt. While sauce is simmering, cook pasta in boiling water until al dente and drain well in a colander. Add pasta to sauce and toss to coat. Divide pasta between 2 bowls and serve with dollops of ricotta on top.