Prep the steak: Pat the steak cubes very dry with paper towels.
Dry meat sears better. Season generously with salt and pepper on all sides.
Preheat the pan: Heat a large cast-iron skillet over medium-high until blazing hot. Add the avocado oil and swirl to coat.
Work in batches: Add half the steak in a single layer, leaving space between pieces. Don’t crowd the pan or they’ll steam.
Sear 2–3 minutes without moving until a deep crust forms.
Flip and finish: Flip the bites and cook another 1–2 minutes for medium-rare to medium. Transfer to a plate and tent loosely with foil. Repeat with remaining steak.
Make the garlic butter: Reduce heat to medium-low.
Add the butter to the pan. Once melted, stir in the garlic. Cook 30–45 seconds, just until fragrant.
Don’t brown the garlic.
Brighten and season: Stir in the lemon juice, smoked paprika, and red pepper flakes if using. Taste and adjust salt and pepper.
Toss and garnish: Return steak bites and any juices to the pan. Toss to coat in the garlic butter for 30 seconds.
Remove from heat and finish with chopped parsley.
Serve right away: Plate with your favorite keto sides or toothpicks for snacking.