Preheat the oven to 425°F (220°C).

Bring a large pot of salted water to a boil over high heat.

Add the rigatoni, and boil until al dente, 8–10 minutes.

Drain, reserving ½ cup of the pasta cooking water. Set aside.

Toss together the tomatoes, oil, salt, and pepper in a bowl.

Arrange evenly on a baking sheet.

Roast in the preheated oven until blistered, about 5 minutes.

Remove from the oven, and set aside.

Melt 6 tablespoons of the butter in a large skillet over medium heat.

Cook, swirling the skillet, until the butter is foamy and golden with brown specks, about 3 minutes.

Add the onion, and cook, stirring often, until translucent, about 1 minute.

Stir in the garlic, and cook, stirring constantly, for 30 seconds.

Stir in the tomato paste, and cook, stirring constantly, until it darkens in color, about 2 minutes.

Add the reserved ½ cup pasta cooking water to the mixture in the skillet.

Cook over low heat, stirring constantly, until the mixture emulsifies and forms a glossy sauce, about 2 minutes.

Add the drained rigatoni to the mixture in the skillet, and toss to coat.

Stir in the remaining 2 tablespoons butter.

Cook over low heat, stirring constantly, until well combined, about 1 minute.

Add the basil and lemon zest, tossing gently to combine.

Divide the pasta evenly among 2 bowls.

Top evenly with the roasted tomatoes.

Sprinkle with the Parmesan, and serve.