01 - Cook pasta according to package directions until al dente. Drain, reserving 1/2 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.
03 - Heat olive oil (or reserved sun-dried tomato oil) in a large skillet over medium heat. Sauté chopped onion for 3-4 minutes until translucent.
04 - Pour the creamy sun-dried tomato sauce into the skillet and bring to a gentle simmer for 3-4 minutes, stirring occasionally.
05 - Add spinach and cook until wilted, about 2 minutes.
06 - Add cooked pasta to the skillet, tossing to combine. Add a splash of reserved pasta water if the sauce is too thick.
07 - Serve immediately, garnished with fresh basil and red pepper flakes if desired.