Bring a large pot of salted water to a boil. Add cheese tortellini and cook according to package instructions until al dente, about 3-5 minutes. Reserve ½ cup of pasta water, drain tortellini, and set aside.

Pat steak dry and season with Cajun seasoning, smoked paprika, garlic powder, salt, and black pepper. Heat 2 tbsp olive oil in a skillet over medium-high heat and sear steak for 2-3 minutes on each side. Remove from skillet and let rest.

In the same skillet, reduce heat to medium and add butter. Once melted, stir in minced garlic and sauté for 1 minute. Add red pepper flakes, Dijon mustard, and lemon juice. Stir in parsley and chives.

Return cooked tortellini and steak bites to skillet. Toss together and gradually add reserved pasta water, mixing until desired consistency is reached. Stir in grated Parmesan cheese.

Serve immediately, garnished with extra Parmesan, parsley, and Cajun seasoning if desired.