In a shallow mixing bowl, whisk together 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.
Add the chicken tenders (or sliced breasts) to the marinade, coat well, and refrigerate for at least 15 minutes.
While the chicken marinates, bring a large pot of salted water to a boil and cook the penne according to package directions until al dente; drain and set aside.
Preheat a grill or grill pan to medium heat. Grill the marinated chicken, covered if using a grill, until browned on one side, about 3–5 minutes, then flip and cook until cooked through (internal temperature 165°F). Transfer to a plate and 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 until fragrant, 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 with salt and freshly ground black pepper to taste.
Toss the cooked penne, diced tomatoes, and chopped parsley into the sauce until evenly coated.
Slice or arrange the grilled chicken over the pasta and sprinkle with freshly grated Parmesan, if desired, before serving.