Bring a large pot of salted water to a boil. Cook the pasta until al dente according to package directions. Reserve 1 cup of pasta water, then drain the pasta.

Pat the steak dry with paper towels. Season both sides with kosher salt, black pepper, garlic powder, and smoked paprika.

Heat olive oil in a large skillet over medium-high heat. Add the steak and sear for 3 to 4 minutes per side for medium-rare, or cook to your preferred doneness.

During the final minute, add butter and sage leaves if using. Spoon the melted butter over the steak.

Transfer the steak to a cutting board, cover loosely with foil, and rest for at least 5 minutes.

Reduce the skillet heat to medium. Add 1 tablespoon butter or olive oil. Add shallot and cook for 2 to 3 minutes until softened.

Add garlic and cook for 30 seconds until fragrant.

Stir in pumpkin purée, chicken broth, heavy cream, sage, thyme, nutmeg if using, salt, and black pepper. Simmer gently for 4 to 5 minutes, stirring often.

Reduce heat to low. Stir in Parmesan cheese until melted and smooth.

Add the drained pasta to the skillet. Toss until coated, adding reserved pasta water a few tablespoons at a time until the sauce is silky and reaches your preferred consistency.

Slice the rested steak thinly against the grain.

Divide pumpkin pasta among bowls and top with sliced steak. Garnish with extra Parmesan, fresh sage, black pepper, and red pepper flakes if desired.