Bring a pot of salted water to a boil and cook the penne pasta until al dente according to package directions.
Season the chicken breast evenly with sea salt, black pepper, and onion powder.
Heat olive oil in a large skillet over medium-high heat and sear the chicken until golden and cooked through, about 5-6 minutes per side.
Add the broccoli florets to the pasta pot during the last 3 minutes of boiling to steam them until tender-crisp.
Carefully reserve 2 tablespoons of the starchy pasta water before draining the pasta and broccoli.
In a small bowl, whisk together the Greek yogurt, parmesan cheese, minced garlic, and the reserved pasta water until the sauce is smooth.
Remove the chicken from the skillet and slice it into thin, bite-sized strips.
Return the drained pasta, broccoli, and sliced chicken to the skillet, pour the yogurt sauce over the top, and toss gently over low heat until well-combined and creamy.