Cut each tomato into quarters and place on a platter with cut sides up.
Sprinkle evenly with salt and set aside.
Preheat a large pan to medium heat.
Pat tuna steak dry with a paper towel then season with salt and pepper.
Add oil to pan and add tuna, gently pressing so the entire surface touches. Sear for 2 minutes.
Using a thin offset spatula, very gently flip the tuna, pressing down gently and searing for another 2 minutes.
When done, transfer tuna to a lipped plate. Pour orange juice and 1 tablespoon of extra virgin olive oil over the entire steak. Flip occasionally and allow to cool to room temperature, about 8 minutes. Reserve juices.
In a small bowl combine parsley, chives, thai child, garlic, and remaining extra virgin olive oil. Pour reserved juices into the bowl and mix.
Using a sharp knife, cut steak against the grain into long strips about 1″ (2.5 cm) wide. Using your hands, gently pull apart at its natural grain lines into chunks the size of a strawberry.
Arrange tomatoes on a platter and garnish with red onion.
Place the steak pieces around the tomatoes and spoon dressing over top.