Brush the tuna steaks with the olive oil and season with salt and pepper. In a hot griddle pan, sear quickly on both sides for 2-3 minutes in total.
In a mixing bowl, add the watercress, rocket, tomatoes, avocado, olive oil and balsamic vinegar and gently mix together. Divide the salad between two plates.
Slice the tuna 2-3 times and lay over the salad. Spoon over a little of the remaining dressing in the mixing bowl and serve.
Notes
Tuna contains vitamin B which is a major component in strengthening bones. This vitamin makes the bones stronger and protects them from injuries.