Bring a large pot of water to a boil. Add the rigatoni and cook according to the package directions until al dente. Add the frozen peas during the final minute of cooking, then drain the pasta and peas and return them to the pot.

While the pasta cooks, heat the olive oil in a large skillet over medium heat. Add the minced onion and cook for about 5 minutes, stirring occasionally, until soft and translucent.

Add the cherry tomatoes and garlic to the skillet. Cook over medium heat, stirring occasionally, until the tomatoes soften and burst and the garlic is golden, about 8–10 minutes. Reduce the heat if the garlic begins to brown too quickly.

Transfer the warm tomato mixture to a food processor or blender. Add the cottage cheese, crushed red pepper flakes, and 1/4 cup of Parmesan, then blend until completely smooth and creamy.

Pour the blended sauce over the rigatoni and peas in the pot. Toss over low heat for 1–2 minutes, just until the pasta is evenly coated and warmed through; avoid boiling the sauce.

Divide the pasta among 4 bowls and top with the remaining 1/4 cup Parmesan cheese and torn basil leaves. Serve immediately.