In a large pot, bring salted water to a boil and cook the pasta according to the package directions until al dente. Before draining, reserve about 1 cup of the pasta cooking water and set aside.
In a large skillet, melt the unsalted butter over medium heat. Once melted, add the minced garlic and sauté for about 1 minute, stirring frequently, until the garlic is fragrant but not browned.
Sprinkle in the red pepper flakes and add the halved cherry tomatoes to the skillet. Cook for 3-4 minutes, stirring occasionally, until the tomatoes begin to soften and release their juices.
Add the fresh baby spinach into the skillet and stir until wilted, which should take about 2 minutes.
Next, add the drained pasta directly into the skillet with the garlic butter sauce and vegetables. Toss everything together to ensure the pasta is well coated. If the mixture appears dry, gradually add the reserved pasta water a little at a time until you achieve your desired consistency.
Stir in the freshly grated Parmesan cheese, along with salt and freshly cracked black pepper to taste. Mix well until the cheese melts into the sauce, creating a creamy texture.
Just before serving, fold in the lemon zest to enhance the dish with a refreshing brightness, and toss everything together once more.
Serve immediately on warm plates, garnished with fresh basil leaves, and sprinkle additional Parmesan cheese on top if desired for an extra cheesy finish.
Notes
Adjust red pepper flakes to taste for desired spiciness.