Heat the oven: Set a rack in the middle of the oven and heat the oven to 425°F. Lightly oil a 2 1/2- to 3-quart baking dish and a large sheet pan.

Roast the eggplant: Put the eggplant cubes on the sheet pan. Drizzle with 2 tablespoons of the olive oil, season well with salt and black pepper, and toss to coat.

Spread the eggplant into a single layer on the sheet pan so the pieces have room to brown.

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.

Start the sauce: While the eggplant roasts, put a large skillet on the stove over medium heat and add 1 tablespoon of the olive oil.

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

Add the garlic and dried oregano to the skillet. Cook for 30 seconds to 1 minute, stirring, until the garlic smells fragrant.

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

Add the drained cannellini beans to the skillet. Season with salt and black pepper, then simmer for 8 minutes, stirring a few times, until the beans are hot and the sauce looks slightly thicker.

Spoon the bean and tomato mixture into the prepared baking dish. Spread it into an even layer.

Add the roasted eggplant to the baking dish and gently fold it into the sauce so the eggplant is mixed through but still keeps its shape.