Place the cubed beef in a large bowl. In a separate bowl whisk together soy sauce, 2 tbs olive oil, brown sugar, Worcestershire sauce, minced garlic, black pepper, and kosher salt until sugar dissolves.

Pour the marinade over the beef, toss to coat thoroughly, cover with plastic wrap or a lid and refrigerate for at least 30 minutes and up to 4 hours. Remove beef from refrigerator 20 minutes before cooking to come closer to room temperature.

Vegetables & Garnish

While the beef marinates, toss onion wedges, red bell pepper pieces and baby carrots with 1 tbs olive oil and a pinch of salt and pepper. Set aside.

Searing & Finishing

Heat a large heavy skillet or cast-iron pan over high heat until very hot, about 3-4 minutes. Add 1 tbs olive oil (from marinade section if needed). Working in a single layer and in batches to avoid crowding, add beef cubes to the pan and sear without moving for 1.5-2 minutes to develop a brown crust. Turn and sear other sides for an additional 1-2 minutes, about 3-4 minutes total per batch for medium-rare to medium depending on cube size. Transfer seared beef to a plate; repeat until all beef is seared.

Reduce heat to medium. Add 1 tbs unsalted butter to the skillet and then add the prepared vegetables. Sauté vegetables, stirring occasionally, until onions are translucent and peppers are tender-crisp, about 4-5 minutes.

Return seared beef and any accumulated juices to the pan with vegetables. Pour in 1/2 cup beef stock and bring to a gentle simmer, scraping up browned bits from the bottom of the pan with a wooden spoon.

If you prefer a thicker sauce, mix 1 tsp cornstarch with 1 tbs cold water until smooth and stir into the simmering pan. Cook 1-2 minutes until sauce thickens and coats the beef and vegetables. Taste and adjust seasoning with salt and pepper as needed.

Stir in chopped fresh parsley and remove from heat. Let rest 2-3 minutes so juices redistribute.