Preheat the oven to 425°F (220°C) and line a baking pan with parchment paper.
Rub the potatoes with olive oil and sprinkle all sides with sea salt. Place them on the prepared pan. Bake for about 50-60 minutes, or until tender when pierced with a fork.
Prepare the steak: Trim excess fat from the steak and cut it into 2″ pieces. Drizzle with 2 tablespoons of avocado oil. Liberally coat with cajun seasoning.
Cook the steak: In a cast iron or regular skillet, heat 2 tablespoons of avocado oil over medium-high heat. Cook the steak undisturbed for about 2 minutes, or until golden. Flip and cook for an additional minute, then reduce heat to low and cook for another minute.
Add garlic butter: Move the steak to one side of the pan. Add 2 tablespoons of butter and 1 tablespoon minced garlic to the other side. Sauté until fragrant. Toss the steak in the garlic butter and cook for another minute. Remove the steak and tent with foil to keep warm.
Make the Parmesan Cream Sauce: In the same pan, add 2 more tablespoons of butter and remaining 1 tablespoon garlic. Sauté until fragrant. Slowly whisk in the heavy cream and bring to a simmer. Let it reduce for 3-5 minutes. Add red pepper flakes and parmesan cheese, whisk until the sauce thickens. Adjust salt and pepper as needed. Off the heat, stir in parsley and lemon juice.
Finish the potatoes: Lift and drop each potato from about 12″ off the pan to fluff the inside. Cut the potatoes down the center to open. Fluff with a fork and spread with remaining butter.