01 -
Bring a large pot of salted water to a boil. Add and cook the spaghetti according to package instructions, approximately 9 to 10 minutes. Reserve 1 cup of pasta water before draining and do not rinse.
02 -
In a large skillet over medium heat, melt the unsalted butter. Add the minced garlic and red pepper flakes, stirring and cooking until fragrant, about 30 seconds to 1 minute.
03 -
Add the lemon juice and ½ cup of reserved pasta water to the skillet. Once it begins to bubble, add the baby spinach and cooked pasta. Toss together until the spinach wilts and the sauce coats the noodles. If the sauce seems dry, add ¼ cup of pasta water as needed.
04 -
Remove the skillet from heat. Add the lemon zest, parmesan cheese, salt, and black pepper. Toss a few times and serve immediately.