Prepare the salmon: Combine 4 cups water, the sugar, 2 cups salt and the lemon juice in a large saucepan and bring to a boil, stirring to dissolve. Remove from the heat and let cool, then refrigerate until cold, about 30 minutes. Add the salmon; brine in the refrigerator, 2 hours.
Preheat the oven to 400 degrees F. Remove the salmon from the brine and pat dry. Brush with olive oil on both sides. Place in a roasting pan and bake until just opaque, about 14 minutes. Let cool, then flake with a fork.
Make the dressing: Whisk the lemon juice, vinegar and honey in a small bowl. Slowly whisk in the olive oil until emulsified. Season with salt.
Combine the arugula, chives, celery leaves, parsley and fennel in a large bowl and toss with the dressing. Divide among plates and top with the salmon.
Photograph by David Malosh
Recipe courtesy Geoffrey Zakarian for Food Network Magazine