Preheat oven to 400 degrees. Prepare a rimmed baking sheet with aluminum foil and spray with nonstick cooking spray.

Toss cubed butternut squash with half of the olive oil (1 tablespoon) and season as desired with salt and pepper. Bake in the oven for 30 to 40 minutes (depending on the size of the squash cubes) or until the squash is softened. Tip: During the last 5 minutes of baking time, add the walnuts to one corner of the baking sheet to toast lightly.

Meanwhile, cook spaghetti according to package instructions. Drain and return to pot. Toss with lemon juice.

While the pasta is cooking, heat the remaining tablespoon of olive oil in a skillet over medium-high heat. Stir in garlic and red pepper flakes, cooking until fragrant.

Add the heavy cream and bring to a simmer. Stir in spinach.

Stir in parmesan cheese and cooked butternut squash.

Pour sauce over drained spaghetti and toss to combine. Serve topped with chopped walnuts, additional grated Parmesan, and lemon zest if desired.