1. Cook the frozen ravioli or tortellini of your choice in a pot of salted boiling water according to package instructions. Reserve 1 cup of pasta water before draining.
2. Melt the butter in a large skillet. Add the garlic, crushed red pepper and sage and cook over moderate heat, stirring occasionally, until fragrant, about 30 seconds.
3. Whisk in heavy cream, pumpkin purée and lemon juice until smooth. Simmer the sauce until thick enough to coat the back of a spoon, about 10 minutes.
3. Stir in the parmesan cheese until smooth. Season with salt.
4. Add the cooked pasta to the sauce and toss to coat. If the sauce is too thick, add some of the reserved pasta water.
5. Spoon the pasta into four shallow bowls. Garnish with shaved parmesan cheese, toasted pepitas, and fresh sage, if using. Sprinkle with more crushed red pepper and enjoy!