Prepare the Beef: Season the sliced beef strips with salt, pepper, and a sprinkle of thyme.

Sear the Beef:
• Heat a tablespoon of olive oil in a large skillet over medium-high heat.

Add the beef strips, searing them on each side until browned but still pink in the middle (about 2 minutes per side). Remove and set aside.

Sauté the Veggies:
• In the same skillet, add a bit more olive oil and butter. Add the onions and garlic, and cook until fragrant and soft.

Add the bell peppers and cabbage, stirring occasionally until everything is caramelized and tender (about 7-10 minutes).

Stir in soy sauce and balsamic vinegar, letting the mixture cook for another 2-3 minutes to deepen the flavor. Season with salt, black pepper, and red pepper flakes for a subtle heat.

Combine and Finish:
• Add the seared beef back to the skillet, stirring everything together so the flavors meld.

Cook for another minute or so until the beef is just heated through.