Cut avocados in half and remove pits. Squeeze lemon juice onto all 4 avocado halves, rub gently to coat avocados.
In a medium bowl combine tomato quarters, feta, red onion, vinegar, oil, and basil leaves
Top avocado halves with tomato mixture\
You can cut a silver of the base of the avocado off to create a smooth base so that avocado halves balance.