Place cubed meat into a large mixing bowl, add onion powder, garlic salt, and Montreal steak seasoning. Add half of the olive oil and toss to coat.
Heat remaining olive oil in skillet over medium-high heat until shimmering.
A beef cubes and brown on all sides, cooking for 2-3 minutes per side undisturbed to allow them to brown nicely. Remove beef from skillet and set aside.
Add garlic and butter to skillet, cooking until butter is almost melted. Whisk constantly, sprinkle in cornstarch.
Add beef cubes back to the skillet, toss to coat and warm through.
You'll want to stick to lean, tender cuts when making steak bites. Sirloin is your best bet for this, however, tenderloin and ribeye are other great options.
Chef Antoine suggests when cutting and trimming the roast, try to cut along the fat lines then trim. This will give you the most tender cubes without fat or connective tissue running through your cubes of meat.
We use salted butter in our savory recipes and unsalted butter in our sweet dessert recipes. For savory recipes you can use either one. If you want to use salted butter, we suggest using a small amount of garlic salt in the recipe.