Place tomatoes, cucumbers and onions in a large bowl, set aside.
In a mixing cup or small bowl, add olive oil, balsamic vinegar, lemon juice, sugar, Italian seasoning, garlic, salt and pepper. Using a whisk, blend until well mixed. Pour dressing over tomatoes, cucumbers and onions. Toss salad.
Can be served immediately or stored in the fridge, covered for up to 2 days.
***If making the salad ahead of serving, use half of dressing to toss salad and reserve half to add in later.