Bering 3 cups of water to boil on the stovetop in a medium-sized pan. Combine barley and reduce to simmer for 30-45 minutes until barley is tender and liquid is absorbed. Stir occasionally.
Slice cucumbers into half-moons, dice the tomato and slice the onion. Combine in a medium-sized bowl.
In a small bowl, combine all ingredients for the dressing and whisk together.
Once the barley is done, mix well with the vegetables. Pour dressing on top and combine. Serve either immediately or put in the fridge and enjoy later!