Dressing. In a small bowl combine all the ingredients for dressing: Greek yogurt, olive oil, Dijon mustard, lemon juice & salt.
Assembling the salad. In a large bowl make a bed for salad using the iceberg lettuce.
Place tuna, cucumber, eggs, avocados, whole kernel corn on the lettuce. Add in the sliced red chili & red chili flakes( optional).
Pour in the salad dressing. Mix all together, tossing to coat.
Avocado tuna salad is ready to serve!