Combine all of the Cajun spices in a mixing bowl and mix thoroughly.
Cut the meat into cubes. (1 1/2-2" or so)
Add the steak chunks to the bowl of spices and mix. Ensure that all the cubes are covered with the spice mixture. Make sure to scrape the spices up from the bottom - you don't want to waste any of that flavor.
Heat a large skillet on medium heat. Ensure that it's hot before you start searing the meat.
Once the pan is all the way hot-hot, add olive oil and add the meat. Meat should be in one layer on the bottom of the pan. Sear the steak for 2-5 minutes per side until the edges are crispy and brown. If your pan is not big enough for this you can divide the oil and meat and cook it in two batches. (2 minutes per side will be pretty rare, and 5 minutes will be well done)
When you're done searing the steak remove it and set aside.
Reduce the heat to low and add the butter to the skillet. You may want to scrape the bottom of the pan with a spatula, but don't remove any of the oil left there - it is very flavorful.
Once the butter is melted turn off the heat and put the meat back in the pan and toss it to evenly coat all the pieces with butter. If you are using fresh garlic and/or onion add it once the butter is melted and sauté for about a minute or so (until fragrant) then turn off the heat and toss the steak in the garlic/onion butter.
Nutrition
Calories: 426kcal | Carbohydrates: 6g | Protein: 21g | Fat: 36g | Sodium: 175mg | Fiber: 3g | Net Carbs: 3g | Fat Ratio per Serving: 76.06% | Protein Ratio per Serving: 19.72% | Carb Ratio per Serving: 2.82%