01 - Bring a large pot of salted water to boil. Cook pasta according to package directions until al dente. Drain, reserving 0.5 cup of the cooking water. Set aside.
02 - Combine soaked cashews, drained sun-dried tomatoes, plant-based milk, nutritional yeast, garlic, lemon juice, oregano, salt, and black pepper in a high-speed blender. Blend on high speed until completely smooth and creamy, approximately 1-2 minutes.
03 - Heat olive oil or reserved sun-dried tomato oil in a large skillet over medium heat. Add finely chopped yellow onion and sauté for 3-4 minutes, stirring frequently, until translucent and fragrant.
04 - Pour the blended sun-dried tomato sauce into the skillet with the onions. Bring to a gentle simmer over medium-low heat and cook for 3-4 minutes, stirring occasionally to prevent sticking.
05 - Add fresh baby spinach to the simmering sauce. Cook for approximately 2 minutes, stirring gently, until spinach is completely wilted and incorporated into the sauce.
06 - Add cooked pasta to the skillet and toss thoroughly to coat with sauce. If sauce appears too thick, add a splash of reserved pasta water to achieve desired consistency.
07 - Plate immediately, garnished with torn fresh basil leaves and crushed red pepper flakes if desired. Serve while hot for optimal texture and flavor.