To prepare vinaigrette, combine first 5 ingredients in a small bowl. Slowly add olive oil, stirring constantly with a whisk. Set aside.
To prepare salmon, combine 1 cup water, sake, and ginger in a large saut pan over medium-high heat; bring to a boil. Reduce heat, and add salmon to pan. Cover and simmer 6 minutes.
Remove salmon and ginger from pan. Discard the ginger.
Add Swiss chard and spinach to pan; cook 2 minutes or until wilted. Stir in salt and pepper. Divide the spinach mixture evenly among 4 plates. Top each serving with 1 salmon fillet; drizzle each serving with 2 tablespoons vinaigrette.
Wine note: With the lively and abundant acidity of lemon juice, rice wine vinegar, and sake, this dish needs a bright, fresh wine to match. Try an affordable Austrian grner veltliner like Loimer Lois 2006 ($14), with its refreshing lemon-lime and grapefruit flavors, and hints of English peas and beeswax. The slightly green, herbal finish permits it to complement the Swiss chard. Jeffery Lindenmuth