In a large pot, bring salted water to a boil. Add the linguine and cook according to package instructions until al dente. Reserve 1 cup of the pasta water, then drain and set aside.

In a large skillet, melt half of the butter over medium heat. Add the diced chicken, season with salt and pepper, and cook until golden and cooked through (about 5-7 minutes). Remove the chicken and set aside.

In the same skillet, melt the remaining butter. Add the chopped onion and sauté until translucent. Stir in the minced garlic and red pepper flakes, cooking for an extra minute until fragrant.

Add the chicken back to the skillet, and pour in the lemon juice. Stir to combine. Slowly add the cooked linguine, mixing thoroughly to ensure the pasta is well-coated. If the sauce seems too thick, add some reserved pasta water until you reach your desired consistency.

Remove from heat, and stir in the parsley for a fresh touch. Taste and adjust seasoning if necessary.

Dish out the Cowboy Butter Chicken Linguine onto plates, garnish with extra parsley, and a sprinkle of grated cheese if desired. Enjoy hot and fresh!