Bring a large pot of generously salted water to a boil. Add the gnocchi and cook according to package instructions (typically 2-3 minutes or until they float to the surface). Before draining, reserve 1/4 cup of pasta water for the sauce. Drain the gnocchi and set aside.
In a large skillet, heat olive oil over medium heat. Add the diced onion and cook for 3-4 minutes until translucent. Add minced garlic and cook for an additional 30 seconds until fragrant (but not browned).
Add the crushed tomatoes to the skillet, along with a pinch of salt, black pepper, and red pepper flakes (if using). Let the sauce simmer for 5-7 minutes until it starts to thicken slightly and the flavors meld together.
Reduce heat to low and stir in the heavy cream. Allow the mixture to simmer gently for 2-3 minutes until the sauce takes on a beautiful orange-pink hue. Be careful not to boil the cream.
Add the cooked gnocchi to the sauce, gently tossing to ensure each piece is coated. Stir in the torn basil leaves and Parmesan cheese until well incorporated. If needed, add a splash of reserved pasta water to loosen the sauce.
Serve immediately, garnished with additional fresh basil and grated Parmesan cheese.