Bring a large pot of salted water to a boil and cook the pasta until just al dente, about 8 minutes. Drain and set aside, saving a cup of pasta water.
While the pasta boils, heat the olive oil in a large skillet over medium heat. Add crushed garlic and sauté for about 30 seconds until fragrant and golden, filling your kitchen with a sweet, nutty aroma.
Add the fresh spinach to the skillet, stirring until it wilts and turns a vibrant dark green, about 1-2 minutes. The spinach should release a fresh, earthy aroma and become tender.
Reduce the heat slightly and toss in the cooked pasta, stirring to coat the noodles with the garlic and spinach mixture. The pasta should shimmer with the flavorful oils and greens.
Crumble the feta cheese over the pasta and gently stir to combine. Allow the feta to start melting slightly, creating streaks of salty, tangy creaminess. If the mixture feels dry, add a splash of reserved pasta water to loosen and create a silky sauce.
Finish by squeezing fresh lemon juice over the pasta and adding freshly cracked black pepper. Taste and adjust seasonings as needed, then remove from heat.
Serve immediately while warm, garnished with extra feta or herbs if desired. The dish should be vibrant, creamy, and fragrant, perfect for a cozy, quick meal.