Pre-heat oven to 400°. Place salmon fillet skin side down on a parchment lined baking sheet. Sprinkle the fish with dill, lemon zest, salt and pepper and press into the fish.
Bake the salmon until the flesh is opaque throughout and flakes easily with a fork. Depending on the thickness of your fillet, it should only take 7-10 minutes.
Remove salmon from oven and break into chunks with a fork. The fish will easily come off of the skin, which can be discarded.
While the salmon is cooking, cook pasta al dente in a large pot of water until , usually 8-10 minutes, but check your package directions.
Scoop out and reserve a cup of the pasta water, then drain the pasta into a colander.
Return pasta to pot, and over low heat, add spinach, tossing until leaves are just wilted. Add Greek yogurt, lemon juice and red pepper flakes and toss to coat pasta. Use the reserved pasta water to thin sauce if needed.
Add salmon and toss again gently until everything is coated with sauce, remove from heat and serve.
Notes
If you have a larger piece of salmon, cut it into smaller pieces before baking. This will allow for quicker cooking.