Whisk the olive oil, lime juice, chili powder, brown sugar, cumin, paprika, onion powder, garlic powder, 1 teaspoon salt, 1/2 teaspoon black pepper and a pinch of cayenne in a shallow bowl to make the marinade.
Add the chicken tenders (or sliced breasts) to the marinade, toss to coat, and marinate for at least 15 minutes.
Meanwhile, cook the penne in a large pot of salted boiling water according to package directions until al dente, then drain and set aside.
Heat a grill or grill pan over medium heat and lightly oil the grates. Grill the marinated chicken, covered if possible, until browned on the first side and cooked through after flipping, about a few minutes per side depending on thickness. Transfer to a plate and let rest.
In a large skillet over medium-high heat, melt the butter. Add the chopped onion and cook 3–4 minutes until softened.
Add the minced garlic and cook 30 seconds, then sprinkle in the flour and stir to combine to form a roux.
Slowly whisk in the chicken broth and milk until smooth, then add the cubed cream cheese and stir until melted and the sauce is creamy.
Season the sauce with salt and freshly ground black pepper to taste.
Add the cooked penne, diced tomatoes, and chopped parsley to the skillet and toss to coat evenly with the sauce.
Slice or place the grilled chicken on top of the pasta and sprinkle with freshly grated Parmesan, if using, before serving.
