Bring a large pot of salted water to a boil, then add your pasta and cook until al dente, about 8-10 minutes. Drain and set aside.
While the pasta cooks, heat the olive oil in a large skillet over medium heat. Add the chopped onion and sauté, stirring frequently, until it becomes translucent and fragrant, about 3-4 minutes.
Add the minced garlic to the skillet and cook for another minute until it releases a fragrant aroma, making sure not to burn it.
Stir in the chopped tomatoes and a pinch of salt. Let the mixture simmer gently, stirring occasionally, until the tomatoes break down and release their juices, about 10 minutes. The sauce will thicken slightly and smell sweet and smoky.
Meanwhile, drain and rinse your soaked cashews. Transfer them to a high-speed blender along with water, lemon juice, and a pinch of salt. Blend until completely smooth and creamy, about 1-2 minutes.
Once the tomato sauce has thickened, stir in the cashew cream. Let it simmer together for another 2 minutes, allowing the flavors to meld and the sauce to become velvety.
Drain the cooked pasta, reserving a little of the pasta water. Toss the pasta into the skillet with the sauce, adding a splash of reserved water if needed to loosen it up and help it coat every strand evenly.
Taste the pasta and sauce, then adjust with salt or pepper as needed. Off the heat, stir in the chopped basil for a fresh, fragrant finish.
Serve immediately, garnished with extra basil leaves and a drizzle of olive oil if desired. Enjoy the vibrant, creamy bites that balance brightness with indulgence.