Bring a large pot of salted water to a boil. Cook bowtie pasta according to package directions until al dente.
Add broccoli florets during the last 3 minutes of cooking. Reserve ½ cup pasta water, then drain and set aside.
Season chicken with Cajun seasoning, garlic powder, smoked paprika, salt, and pepper.
Heat olive oil in a large skillet over medium-high heat. Cook chicken until golden and cooked through, about 6–7 minutes. Remove and set aside.
Lower heat to medium and add butter to the skillet. Once melted, add garlic and cook until fragrant.
Stir in red pepper flakes, Dijon mustard, lemon juice, and lemon zest. Season with salt and pepper.
Return chicken, pasta, and broccoli to the skillet. Toss to coat. Add reserved pasta water as needed.
Stir in Parmesan cheese until melted and creamy.
Serve warm with extra Parmesan and fresh herbs.
