Line plate with double-lined paper towel, and sprinkle salmon with salt. Place salmon in saucepan with lime leaves (if using) and cover with cold water; bring to a low boil over medium heat. Reduce heat to low, cover and simmer until barely cooked through, about 3 to 5 minutes. Using a slotted spoon, transfer salmon to prepared plate and refrigerate until ready to use.

In high-speed blender, combine lime juice, cilantro, basil, jalapeno and apple; purée to combine. Add avocados and cucumber; pulse to combine. With blender on low speed, slowly stream in olive oil and then water until smooth. Season with salt to taste. Refrigerate gazpacho for at least 1 hour or up to overnight to allow flavours to bloom.

Break reserved salmon into bite-size chunks. Divide gazpacho among bowls and top with salmon, cucumbers, green onions and olive oil.