Cook the spaghetti according to package directions in well-salted boiling water until al dente. Reserve about 1.5 cups of the pasta water before draining.

While the pasta cooks, heat the olive oil in a large skillet over medium heat. Add the chopped garlic scapes and red pepper flakes. Cook, stirring occasionally, for about 5-7 minutes, or until the scapes begin to soften and turn bright green.

Add the butter to the skillet with the garlic scapes and let it melt. Continue to cook for another 2-3 minutes until the garlic scapes are tender but not browned.

Add the drained spaghetti to the skillet with the garlic scapes. Toss to combine.

Pour in about 1 cup of the reserved pasta water, the lemon zest, lemon juice, and grated Parmesan cheese. Stir vigorously to create a light sauce. Add more pasta water, a tablespoon at a time, if needed to reach your desired consistency.

Season generously with salt and freshly ground black pepper to taste. Toss again to ensure everything is well combined.

Serve immediately, garnished with fresh parsley and additional grated Parmesan cheese, if desired.