In a pot or Dutch oven over medium-high heat, melt the butter. Add diced shallots and minced garlic as the butter melts.
Sprinkle in the crushed red pepper and mix well. Let the shallots and garlic soften for 1-2 minutes, stirring frequently to prevent sticking or burning.
Add the uncooked pasta to the hot pan, followed by marinara sauce, broth, and salt. Mix everything together and bring it to a gentle boil to cook the pasta. Cover and reduce the heat to medium-low, letting it cook for about 12-13 minutes.
Once the rigatoni is perfectly cooked, stir in the heavy cream, peas, and Parmesan cheese. Mix over medium heat until the sauce comes together. Serve immediately, and feel free to garnish with fresh herbs and an extra sprinkle of Parmesan! Enjoy your delightful one-pot wonder.