Bring a large pot of salted water to a boil. Add the spaghetti and cook according to package instructions until al dente. Drain and set aside.

In a skillet over medium heat, add olive oil. Once hot, add the sliced chicken breasts. Season with salt and pepper. Cook until golden brown and cooked through, about 5-7 minutes. Remove from skillet and set aside.

In the same skillet, add minced garlic and red pepper flakes. Sauté for about 1 minute until fragrant. Add lemon juice, lemon zest, and chicken broth. Bring to a simmer.

Add the cooked pasta and chicken to the skillet. Toss to coat everything in the sauce. Cook for an additional 2-3 minutes to heat through.

Serve immediately, garnished with chopped parsley and grated parmesan cheese.