Boil a large pot of salted water. Cook the penne pasta for 10-12 minutes until al dente, then drain and reserve some pasta water.

In a bowl, combine steak strips with olive oil, Cajun seasoning, garlic powder, smoked paprika, salt, and pepper. Toss to coat and let sit for 5 minutes.

Heat a skillet over medium-high, add butter, and sear the steak for 2-3 minutes per side until golden brown, then remove and let it rest.

Add more butter to the skillet, sauté minced garlic for about 30 seconds until fragrant, then remove from heat.

Whisk in flour to the skillet, then gradually add heavy cream and milk, stirring until the sauce thickens for about 3-5 minutes.

Reduce heat and add cheeses, stirring until fully melted and creamy.

Combine cooked pasta with the sauce, adding reserved pasta water to adjust consistency, and heat through.

Plate the pasta, top with seared steak, and garnish with parsley, cheese, and red pepper flakes.