Add onions and cauliflower. Cover and cook about 10 minutes or until cauliflower is tender, stirring occasionally. If pan becomes too dry, add water, 1-2 Tbsp at a time.
Add in remaining ingredients: Remaining 2 tsp olive oil, Tomatoes, garlic, Balsamic vinegar, pepper, salt, and chili powder, and stir well.
Cook uncovered about 3 minutes, stirring occasionally.