Bring a large pot of salted water to a rolling boil. Add the pasta and cook until just al dente, about 8 minutes, until it has a slight resistance when bitten. Drain and set aside, reserving a small cup of pasta water.
While the pasta cooks, heat olive oil in a large skillet over medium heat. Add the finely chopped spinach stems and sauté for about 2 minutes until they start to soften and release a faint earthy aroma.
Add the minced garlic to the skillet and cook for about 30 seconds until fragrant, stirring constantly to prevent burning. You should smell a warm, pungent aroma filling the kitchen.
Next, add the fresh spinach leaves to the skillet and stir until they wilt down, about 2 minutes. If the mixture looks dry, splash in a little of the reserved pasta water to keep everything moist and shiny.
Pour the drained pasta into the skillet with the greens, tossing gently with tongs to combine everything evenly. Cook together for another 1-2 minutes until the flavors meld and the pasta is coated with the greens and oil.
Squeeze the fresh lemon juice over the pasta and add the nutritional yeast, stirring well to distribute the flavors. Season with salt and black pepper to taste, then give everything a final toss.
Remove the skillet from heat and let the pasta sit for a minute to settle the flavors. Serve immediately, garnished with extra lemon zest or a drizzle of olive oil if desired, and enjoy the vibrant, crunchy-tender bite.
