1. Make the dressing: In a bowl, whisk together balsamic vinegar, mustard, sweetener, salt, pepper, oregano (optional), garlic powder (optional) and olive oil. Set aside or refrigerate for up to 1 week.
6. In a bowl combine the greens, cucumbers, tomatoes, onions, avocado and steak. Add blue cheese or feta (optional). Drizzle with dressing on top. Serve.