Start a large pot of water for the pasta before beginning. Salt the water well and cook the pasta as stated on the package or recipe (for homemade).
Prepare the cedar nuts and garlic spinach sauce while the pasta is cooking.
Heat a frying pan over low-medium. Once the pan is hot, add the nuts (do not add oil). Stir constantly for 2-3 minutes, until the nuts are toasted. Immediately scoop them out of the pan and set aside.
Return the pan to the heat and add the olive oil and garlic. Cook for 1-2 minutes, until the garlic is fragrant and golden.
Stir in the salt, pepper, and pepper flakes.
Turn off the heat and add the spinach, lemon zest, and lemon juice. The spinach will wilt in the pan.
Scoop out some of the pasta water (about 60ml, a ladleful) before draining the pasta, and add it to the pan with the spinach.
Mix the drained pasta with the spinach and garlic sauce and serve immediately, topped with toasted cedar nuts.
Notes
* Start with about 1/2 teaspoon each salt and pepper and add as needed based on your preference.