Heat the oven to 450°F. Put a large pot of water on the stove over high heat and bring it to a boil for the pasta.

Put the cubed eggplant on a large sheet pan. Drizzle it with 2 tablespoons of the olive oil and toss until the cubes are lightly coated.

Spread the eggplant into a single layer on the sheet pan. Sprinkle it with salt and black pepper.

Roast the eggplant for 20 to 25 minutes, stirring once halfway through, until the cubes are browned at the edges and soft in the center.

When the water reaches a full boil, add a generous spoonful of salt. Add the rigatoni to the pot and stir right away so it does not stick.

Cook the rigatoni until it is just tender but still has a little bite, following the package time and starting to check about 1 minute early.

While the pasta cooks, pour the remaining 2 tablespoons of olive oil into a large skillet or wide saucepan and set it over medium heat.

Add the chopped onion to the skillet. Cook for 5 to 6 minutes, stirring now and then, until the onion is soft and lightly golden.

Add the sliced garlic to the skillet. Cook for about 30 seconds, stirring, until it smells fragrant but has not browned.

Pour the crushed tomatoes into the skillet. Stir well and bring the sauce to a gentle bubble.

Lower the heat to medium-low. Simmer the sauce for 8 to 10 minutes, stirring once or twice, until it looks a little thicker and the oil starts to blend into the tomatoes.

Before you drain the pasta, scoop 1 cup of the pasta cooking water into a mug or measuring cup and set it near the stove.