Start by cutting the beef sirloin into 1-inch cubes, quarter the red onion and wash the cherry tomatoes and mushrooms thoroughly. If using wooden skewers, soak them in water for 30 minutes.

In a large bowl, combine soy sauce, olive oil, lemon juice, Worcestershire sauce, grated garlic, basil, and ground pepper. Mix well.

Add the cubed beef to the marinade, making sure each piece is well coated. Refrigerate for at least 15 minutes.

Thread the marinated beef cubes onto soaked skewers, alternating with red onion, cherry tomatoes, and mushrooms.

Preheat grill to medium-high heat (375°F to 400°F) and lightly grease the grates.

Place the skewers on the grill and cook for 10-15 minutes, flipping halfway through until beef reaches 140°F to 145°F.

Remove from grill, let rest for a few minutes, then serve hot with side dishes.