Boil salted water and cook penne until al dente according to package directions.
Reserve 1 cup pasta water before draining and keep pasta warm in covered pot.
Melt butter in large skillet over medium heat, whisk in flour until smooth, and cook 1-2 minutes until light brown.
Gradually whisk in chicken broth until smooth.
Add garlic, lemon juice, Italian seasoning, salt, pepper, and mustard powder, whisking frequently for 2-3 minutes until slightly thickened.
Stir in sun-dried tomatoes and heavy cream, cooking 5 minutes until simmering and creamy.
Add Parmesan and cream cheese, stirring until melted and smooth.
Stir in spinach until wilted, about 30 seconds.
Add cooked pasta to skillet and toss to coat, adding reserved pasta water as needed to reach desired consistency.
Serve immediately with extra Parmesan and fresh basil if desired.