Cut the beef round into 5 cm cubes.

Let the beef cubes rest at room temperature.

Sprinkle the beef cubes with black pepper.

Brown the beef cubes on all sides over medium-high heat for about 1 minute 30 seconds per piece, with 30 seconds for the end bits.

Place the browned beef cubes into a plastic bag.

Pour the ponzu sauce into the bag with the beef.

Let the beef marinate in the ponzu sauce at room temperature for 15 minutes, turning the bag over occasionally to ensure even flavoring.

If not serving immediately, store the marinated beef in the refrigerator.

Slice the beef thinly before serving.

Serve the sliced beef with your choice of sauces and toppings.

For enhanced flavor, allow the beef to rest in the refrigerator before slicing and serving.