Season the chicken with Italian seasoning, paprika, garlic powder, 1/2 tsp salt, and pepper. Sear in olive oil over medium-high heat, 5-6 minutes per side, until the internal temperature hits 165°F (USDA safe temp — use a thermometer, don’t guess). Rest 5 minutes, then slice. (Resting keeps the juices in the meat instead of on the cutting board.)
Cook the pasta in well-salted boiling water until al dente. Reserve 1 cup pasta water, then drain.
In the same skillet, melt the butter over medium heat. Add the garlic and red pepper flakes; cook 1 minute until fragrant but not browned.
Pour in the broth and simmer 2 minutes, scraping up the browned bits. Add the pasta and 1/2 cup pasta water; toss.
Off the heat, add the Parmesan a handful at a time, then stir in the Greek yogurt and lemon juice until smooth and creamy. (Off-heat is the trick — yogurt + high heat = curdled sauce.)
Fold in the sliced chicken and parsley. Loosen with more pasta water if needed. Serve with extra Parmesan.