Bring a large pot of salted water to a boil, then cook your pasta until al dente, about 8-10 minutes. Drain, reserving ½ cup of the starchy pasta water, and set both aside.
While the pasta cooks, heat olive oil in a skillet over medium heat and gently sauté the minced garlic until fragrant and lightly golden, about 30 seconds to 1 minute. The garlic should release a warm, nutty aroma.
Add a generous handful of fresh spinach to the skillet and cook until wilted, about 2 minutes. The leaves should turn bright green and shrink down, releasing a fresh aroma.
Transfer the sautéed garlic and spinach to a blender. Add the soaked cashews, nutritional yeast, lemon juice, and a pinch of salt. Blend until completely smooth, adding reserved pasta water a little at a time to achieve a silky, vibrant green sauce.
Pour the creamy green sauce back into the skillet over low heat. Toss in the cooked pasta and stir gently until the sauce coats each strand evenly. If the sauce is too thick, add more reserved pasta water, a splash at a time, until it reaches your desired consistency.
Taste the pasta and adjust the seasoning with more salt or lemon juice if needed. Once everything is beautifully coated and fragrant, remove from heat and serve immediately, garnished with extra nutritional yeast or lemon zest if desired.
