Caramelize the Eggplant. Preheat your oven to 425°F (220°C). On a large, rimmed baking sheet, toss the eggplant cubes with 3 tablespoons of the olive oil and ½ teaspoon of kosher salt until evenly coated. Spread into a single layer and roast for 25-30 minutes, flipping halfway through, until deeply golden brown and tender.
Build the Aromatic Foundation. While the eggplant roasts, heat the remaining 3 tablespoons of olive oil in a large Dutch oven or heavy-bottomed pot over medium heat. Add the onion, carrot, and celery. Sauté, stirring occasionally, for 8-10 minutes, until the vegetables are soft and sweet.
Bloom the Spices & Paste. Add the sliced garlic, red pepper flakes, and dried oregano to the pot. Cook for 1 minute until fragrant. Stir in the tomato paste and cook for another 2 minutes, allowing it to toast against the bottom of the pot to develop a rich, deep flavor.
Simmer the Rustic Sauce. Pour in the hand-crushed tomatoes and their juices, add the bay leaf, and season with the remaining ¼ teaspoon of kosher salt. Bring the sauce to a simmer, then reduce the heat to low, cover, and let it gently bubble for 20 minutes to allow the flavors to meld.
Cook the Pasta. As the sauce simmers, bring a large, generously salted pot of water to a boil. Cook the whole wheat rigatoni according to package directions until al dente. Just before draining, reserve about 1 cup of the starchy pasta water.
Combine and Finish. Remove the bay leaf from the sauce. Stir in the fresh lemon juice. Drain the pasta and add it directly to the pot with the sauce, along with the roasted eggplant and half of the torn basil. Toss everything together, adding splashes of the reserved pasta water as needed to create a smooth, emulsified sauce that clings to the pasta.
Serve and Garnish. Divide the pasta among six bowls. Top each serving with a generous grating of ricotta salata, the remaining fresh basil, and a final, light drizzle of extra-virgin olive oil if desired. Serve immediately.