Treat the given proportions below as a guide. If you like a sweeter salad, use more mangoes. Like more tang? Add more tomatoes. If you prefer a stronger bite, go for more onions.
Slice the mangoes to remove the stones. Cut the mango meat into small squares without piercing the skin. Scoop out with a spoon directly into a bowl.
Peel the cucumbers, scoop out and discard the seeds, then cut the cucumber flesh into cubes about the same size as the mangoes.
Cut the mangoes into halves, scoop out and discard the seeds, then cut the flesh into small cubes.
Peel and roughly chop the onions.
Add the cucumbers, tomatoes, onions, scallions and cilantro to the mango in the bowl. Toss gently.
Stir together all the ingredients for the dressing until the no solids are visible.
Drizzle half of the dressing over the contents of the bowl. Toss everything together. Taste. If too bland, drizzle in the remaining dressing and toss a few more times.