Fill a large pot with water, add a generous pinch of salt, and bring it to a rolling boil.
Add the pasta to the boiling water and cook until just al dente, about 8-10 minutes, stirring occasionally. The pasta should be tender yet firm to the bite.
While the pasta cooks, finely mince the garlic cloves and set aside.
In a large skillet, heat the olive oil over medium heat until it shimmers and smells nutty, about 1 minute.
Add the minced garlic to the skillet and sauté until fragrant and slightly golden, about 30 seconds. Be careful not to burn it.
Drain the cooked pasta, reserving about half a cup of starchy pasta water, then add the pasta directly into the skillet with garlic and toss to coat.
Pour in the heavy cream, stirring constantly until the mixture bubbles gently, about 1 minute, creating a velvety sauce base.
Add the chopped spinach and cook, stirring, until wilted and vibrant green, about 2 minutes.
Stir in the grated Parmesan cheese until melted and sauce is smooth. If it thickens too much, loosen with some of the reserved pasta water.
Remove from heat and squeeze in the lemon juice, stirring to brighten the flavors. Add lemon zest if using, for extra freshness.
Taste the pasta and adjust salt or lemon as needed. Serve immediately, garnished with extra Parmesan or lemon zest if desired.
