Heat oven to 400° F. Place salmon fillets on a foil-lined baking sheet. Mix 1 tablespoon of the miso with 1 tablespoon water until well combined. Whisk in 1 tablespoon of the peanut oil and 1/4 teaspoon of the sesame oil. Brush mixture on salmon and roast at 400° F for 15 minutes or until fish flakes easily with a fork.
Blend remaining 1 tablespoon miso with 1 tablespoon water until well combined. Whisk in remaining 1 tablespoon peanut oil and remaining 1/4 teaspoon sesame oil followed by the vinegar and honey. Stir in 2 tablespoons of the scallions.
Divide spinach, snow peas and radishes among 4 plates. Top each with a salmon fillet; garnish with remaining scallions.
Find miso in your market's refrigerated section near the tofu or in the Asian aisle.