Bring a large pot of generously salted water to a boil. Cook linguine until al dente, about 9–11 minutes. Before draining, reserve ¼ cup of pasta water. Drain and lightly toss with olive oil to prevent sticking. Set aside.

While the pasta cooks, mix garlic powder, onion powder, paprika, cayenne (if using), salt, and pepper. Toss over the cubed chicken to coat. Heat olive oil and 1 tbsp butter in a large skillet over medium-high heat. Sear the chicken in a single layer for 3–4 minutes per side, or until golden brown and fully cooked (internal temp of 165°F). Transfer to a plate and tent with foil to keep warm.

In the same skillet (don’t clean it!), reduce heat to medium-low. Add the softened butter and let it melt gently. Stir in minced garlic and sauté for 30–60 seconds until fragrant. Add chicken broth, lemon juice, and Dijon mustard. Whisk and simmer for 2 minutes. Stir in heavy cream and Parmesan until smooth and creamy. Let it simmer gently until the sauce slightly thickens—do not boil.

Return the chicken (with juices) to the skillet. Add the cooked linguine and toss everything together with tongs. Add a splash of reserved pasta water if needed to loosen and emulsify the sauce. Simmer 1–2 minutes for flavors to meld.

Turn off the heat and stir in fresh parsley. Garnish with extra parsley, cracked black pepper, and red pepper flakes if desired. Serve immediately with lemon slices or wedges for a fresh, zesty finish.