Boil the kettle and place cous cous and ¾ cup boiling water in a large container/bowl (allowing enough space for the cous cous to double in volume)
Cover with the container lid or a plate and leave for 5-10 minutes or until the cous cous is soft and water has been absorbed
Dice the red onion, tomato, cucumber and avocado
Drain the black beans, corn, and tuna
Stir/separate the cous cous with a fork, ensuring it does not become clumpy (ie fluff the cous cous)
Add the lemon juice and olive oil to the cous cous and stir through
To serve, place half of each ingredient in each bowl, starting with the cous cous, then the fresh vegetables, tuna, black beans, corn, and sprinkling the sunflower seeds on top