Trim any large visible fat from your top sirloin, then cut the meat into bite-sized cubes—about ¾ to 1 inch works perfectly. Smaller pieces cook through faster; larger pieces stay juicier. In a medium mixing bowl, combine your brown sugar with the kosher salt, black pepper, chili powder, garlic powder, and onion powder. Give it a good stir so everything's evenly distributed. Drizzle your olive oil over the steak pieces, then pour the seasoning mixture on top. Using your hands (this is the fastest and most reliable method), toss everything together until every single piece of beef is coated. You want to see spice clinging to all surfaces. Don't be shy—this is where flavor happens. Set the bowl aside while you preheat your air fryer.

Set your air fryer to 400°F and let it run empty for 5 minutes. This preheating step is non-negotiable. A properly preheated air fryer creates immediate, aggressive heat that sears the exterior of your beef before the inside overcooks. You're building that Maillard reaction from the first second—that's what creates the crust that makes this dish taste expensive. While the air fryer heats, prepare your garlic butter. In a small bowl or ramekin, melt your butter (I do this by letting it sit next to the warm air fryer, or popping it in the microwave for 15 seconds). Stir in the garlic powder, red pepper flakes, parsley, and a pinch of fleur de sel. Set it aside—you'll use this while the steak is still hot.

Once your air fryer beeps that it's ready, carefully add your seasoned steak bites to the basket in a single layer. They can touch slightly, but they shouldn't be stacked. Air frying works through circulating heat, so air needs access to all surfaces. If your basket feels crowded, work in batches—undercooked steak is a tragedy; rushed cooking is never worth it. Set the timer for 4 to 6 minutes at 400°F. Here's where it gets personal: 4 minutes gives you a blushing medium-rare center (my preference). At 5 minutes, you're hitting solid medium. By 6 minutes, you're creeping toward medium-well. I check at the 4-minute mark by cutting into the largest piece. You're looking for a warm, pink center that releases clear juices, not blood. The exterior should be deeply caramelized, almost mahogany in color. This isn't burning—this is flavor development. Any pale spots mean your air fryer temperature wasn't quite hot enough, or you've crowded the basket.

The moment your steak emerges from the air fryer, transfer it to a warm serving bowl or plate. Immediately pour that garlic butter over the hot beef and toss everything together. The residual heat will warm the butter and help it coat every piece, allowing the aromatics to infuse into the beef rather than just sitting on top. Taste one piece. You should experience a wave of umami (that savory, deeply satisfying flavor), followed by warmth from the red pepper flakes, then richness from the butter. If you're craving more salt, add a few flakes of finishing salt. If you want more heat, crack some extra pepper over the top. This is your plate—season it to your joy.