Heat 1 tablespoon olive oil in a large skillet over medium-high heat. Add cubed butternut squash in a single layer and cook undisturbed for 3 to 4 minutes until golden on one side. Add 2 - 3 tablespoons of water to the skillet, cover, and cook for another 5 - 7 minutes,, stirring occasionally, until fork-tender. Remove from heat.
While the squash cooks, cook the pasta according to package directions until al dente. During the last 1 to 2 minutes of cooking, add the frozen peas to the pasta water. Drain the pasta and peas together.
Add the cooked butternut squash, plant-based milk, nutritional yeast, arrowroot powder, remaining 1 tablespoon olive oil, lemon juice, miso, garlic powder, onion powder, smoked paprika, salt, black pepper, and cayenne, if using, to a blender. Blend until smooth and creamy.
Pour the sauce into a large pot or skillet over low heat. Cook for 2 to 3 minutes, stirring often, until warm and slightly thickened.
Add the cooked pasta and peas to the sauce and stir until evenly coated. Warm for another 1 to 2 minutes, stirring often, until creamy and heated through. Serve.