Bring a large pot of salted water to a rolling boil. Cook cheese tortellini according to package directions, usually around 3-5 minutes. Reserve ½ cup of pasta water, then drain and set aside.

Pat the steak dry with paper towels. Season with Cajun seasoning, smoked paprika, salt, and black pepper. Heat olive oil in a skillet over medium-high heat and sear steak bites for 2-3 minutes per side. Remove from skillet and let rest.

In the same skillet, reduce heat to medium and melt butter. Stir in minced garlic and sauté for 30 seconds. Add red pepper flakes, Dijon mustard, and lemon juice, stirring until smooth.

Return the cooked tortellini and steak bites to the skillet with the sauce. Toss gently for about 2-3 minutes, adding reserved pasta water as needed to achieve a creamy consistency. Mix in grated Parmesan cheese until melted.

Remove the skillet from heat. Plate the dish hot, garnishing with extra Parmesan and fresh herbs.