To a large bowl, add tomatoes, avocados, cucumbers, red onion and cilantro. Whisk remaining ingredients in a measuring cup. Taste and adjust salt or sugar per your liking. Pour dressing over vegetables and mix well.
Serve the same day you make this salad. To make ahead the day before, cut up all the ingredients except avocado and put in the serving bowl. The day of, cut the avocados and mix with the dressing. Enjoy :)