In a large pot of salted boiling water, cook the spaghetti 1 minute less than package directions indicate. Reserve 1 cup pasta water, then drain pasta and set aside.
In a skillet over medium-high heat, melt the butter. Add garlic and cook 1 minute, before stirring in zucchini, salt, and red pepper.
Cook, stirring occasionally, for 13-15 minutes. Zucchini liquid will cook off and then the squash will become concentrated.
Stir frequently for 2 minutes more, using the edge of your spatula to chop mixture down into an almost spreadable consistency.
Stir in 1/2 cup of the reserved pasta water, then add the drained pasta, and cook for 2 minutes.
Using tongs, pull the zucchini sauce throughout the pasta strands, adding more water as needed to loosen the mixture.
Add half of the parmesan and basil and mix, then transfer to a serving dish. Top with remaining parmesan and basil and enjoy!
