Cook the Pasta: In a large pot of salted boiling water, cook the linguine pasta according to the package instructions. Drain and set aside, reserving a little pasta water.
Cook the Chicken: In a large skillet, heat olive oil and 1 tablespoon of butter over medium-high heat. Season the chicken cubes with garlic powder, onion powder, smoked paprika, cayenne pepper (if using), salt, and pepper. Add the chicken to the skillet and cook until browned and fully cooked through, about 6-8 minutes. Remove the chicken from the skillet and set aside.
Prepare the Cowboy Butter Sauce: In the same skillet, melt the softened butter over medium heat. Add the chicken broth, heavy cream, Dijon mustard, and grated Parmesan cheese. Stir to combine, allowing the sauce to simmer and thicken slightly for 2-3 minutes.
Combine Everything: Return the cooked chicken to the skillet and stir to coat in the sauce. Add the cooked linguine to the skillet, tossing to combine and coat the pasta in the creamy sauce. If the sauce is too thick, add a little reserved pasta water to reach your desired consistency.
Finish and Serve: Stir in the lemon juice, fresh parsley, and crushed red pepper flakes (if using). Taste and adjust seasoning with salt and pepper as needed. Serve your creamy Cowboy Butter Chicken Linguine hot and enjoy!