Bring a large pot of salted water to a rolling boil, then add your pasta. Cook until al dente, about 8-10 minutes, until it has a slight firmness when bitten. Drain and set aside.
While the pasta cooks, heat a skillet over medium heat. Toast the sunflower seeds until they turn golden brown and release a nutty aroma, about 3-4 minutes. Shake the pan frequently to prevent burning.
In your blender, combine the toasted sunflower seeds, fresh basil leaves, garlic, lemon juice, olive oil, and nutritional yeast. Blend until smooth and creamy, stopping to scrape down the sides if needed. If the mixture is too thick, add a splash of water or more olive oil to loosen it.
Taste the pesto and season with salt and pepper. Adjust the lemon juice or seasoning as desired for brightness and balance.
Transfer the cooked pasta back into the large pot or a mixing bowl. Pour the freshly blended pesto over the hot pasta and toss gently to coat evenly. If the pesto is too thick, add a little reserved pasta water to achieve a silky, glossy sauce.
Serve immediately, garnished with extra fresh herbs or a drizzle of olive oil if desired. The pasta should be vibrant, fragrant, and coated in a smooth, herby pesto. Enjoy!
