Heat 1 tbsp olive oil in a skillet over medium heat. Add onions and a bit of salt then saute until golden brown and caramelized – about 15-20 minutes.
In large grill pan, heat the other tablespoon of olive oil over medium high heat and season the chicken breasts with sea salt, freshly cracked pepper, and garlic powder, to taste. Make sure pan is nice and hot before adding the chicken. Cook for 5-6 minutes before turning over. Cook for additional 3-4 minutes to desired degree of doneness. Remove from heat to a serving platter. Make sure to let the chicken rest for 3-5 minutes before slicing so it stays nice and juicy. Slice into thin strips at an angle once it has rested.
In the same skillet as the onions, add the grape tomatoes then season with sea salt and freshly cracked pepper, to taste. Cook for 3-4 minutes until the tomatoes are soft. Add minced garlic, stirring frequently for 60 seconds. Pour the tomatoes and onions on top of the sliced chicken, drizzle with balsamic vinegar. Top with feta cheese and fresh basil.
Source: For the Love of Cooking