Cook the Linguine: Bring a large pot of salted water to a boil. Add linguine and cook until al dente, about 9–11 minutes. Reserve ¼ cup pasta water before draining and toss with olive oil to prevent sticking.

Season the Chicken: In a mixing bowl, combine garlic powder, onion powder, paprika, cayenne, salt, and black pepper. Toss cubed chicken in the spice mix until evenly coated.

Sear the Chicken: Heat olive oil and butter in a skillet over medium-high heat. Add seasoned chicken and sear for 3–4 minutes per side until golden brown. Transfer to a plate and cover with foil to keep warm.

Create the Sauce: In the same skillet, reduce heat to medium-low. Add remaining butter, let it melt, then stir in minced garlic and sauté for 30–60 seconds until fragrant.

Whisk in Broth and Cream: Pour in chicken broth, lemon juice, and Dijon mustard. Whisk and let simmer for 2 minutes. Stir in heavy cream and Parmesan, simmering until slightly thickened.

Combine Everything: Return chicken and juices to skillet. Add linguine and toss together to coat in sauce. If too thick, add reserved pasta water, and simmer for another 1–2 minutes.

Serve and Garnish: Stir in fresh parsley, plate the dish, and garnish with parsley, black pepper, and red pepper flakes if desired. Serve with lemon slices on the side.