Prepare the greens: Remove the outer leaves and any blemished leaves. Tear the leaves in half, and wash.
Combine the tuna, lemon juice, salt and olive oil. Let marinate while preparing salsa.
Prepare the salsa: In a saute pan, heat the olive oil over medium heat. Add the scallions, jalapeno peppers and ginger. Heat until the aroma is released (just 1 to 2 minutes). Add the orange juice and reduce the liquid slightly (3 to 4 minutes). Add the pineapple, herbs and seasonings. Remove from the heat and toss.
In a nonstick pan, sear the tuna on both sides for 4 to 6 minutes, depending on how well done you prefer your fish.
Prepare the garnish: Heat the olive oil to the smoking point and set aside.
Assemble the salad: Toss the greens with enough vinaigrette dressing to coat evenly. Mound the greens along the bottoms of 4 plates with the salsa in the middle of the plate. Lean the tuna fillet on the salsa. Place sliced scallions on top of the tuna and drizzle with the heated olive oil, wilting the scallions and giving off a refreshing aroma.