Soak raw cashews in hot water for at least 15 minutes before blending to ensure a silky-smooth sauce that mimics traditional cream without grittiness.

Toast the dried rosemary briefly in the cooking water before blending to intensify its flavor and prevent the sauce from tasting flat or one-dimensional.

Start with 3-4 tablespoons of nutritional yeast and taste as you go—too much creates a bitter, overly 'cheesy' flavor, while too little lacks the umami depth that makes the sauce satisfying.

Add lemon juice in the final moments of sauce preparation to brighten the dish without losing its acidity to heat, which keeps the sauce from becoming flat and heavy.

Reserve 1 cup of pasta water and toss the hot fettuccine with sauce right away, using pasta water to achieve the perfect silky consistency that clings to each strand.