In a small saucepan, bring the water and a pinch of sea salt to a boil.
Whisk in the corn grits, reduce heat to low, cover, and simmer for 15-20 minutes, stirring occasionally until the texture is velvety.
While the grits cook, drain the tuna, reserving 1 teaspoon of the oil from the can.
Heat the reserved tuna oil in a non-stick skillet over medium-high heat.
Add the tuna to the skillet and sear for 2-3 minutes, stirring occasionally until the edges are crispy and golden.
Remove the tuna from the pan and set aside.
In a small bowl, whisk the whole egg, egg white, garlic powder, and black pepper together.
Wipe the skillet clean, then scramble the eggs over medium-low heat until just set and soft.
Spoon the warm grits into a bowl, top with the seared tuna and scrambled eggs, and garnish with sliced green onions.