01 - Bring a large pot of salted water to a boil. Cook pasta according to package directions until al dente. Drain, reserving ½ cup of the cooking water, and set aside.
02 - Combine soaked cashews, sun-dried tomatoes, plant-based milk, nutritional yeast, garlic, lemon juice, oregano, salt, and pepper in a high-speed blender. Blend until completely smooth and creamy, about 1-2 minutes.
03 - Heat olive oil or reserved sun-dried tomato oil in a large skillet over medium heat. Add chopped onion and cook for 3-4 minutes until translucent and fragrant.
04 - Pour the creamy sun-dried tomato sauce into the skillet with the onions. Bring to a gentle simmer and cook for 3-4 minutes, stirring occasionally to prevent sticking.
05 - Add fresh baby spinach to the skillet and cook until just wilted, about 2 minutes. Stir gently to incorporate evenly into the sauce.
06 - Add cooked pasta to the skillet, tossing thoroughly to coat with the sauce. Add a splash of reserved pasta water if needed to achieve desired consistency. Serve immediately, garnished with torn fresh basil and red pepper flakes if desired.