Step 1

Position rack in upper third of oven; preheat broiler to high. Line a large rimmed baking sheet with foil.

Step 2

Juice 1 lemon and 1 lime into a small bowl. Whisk in miso, oil, maple syrup, pepper and cayenne. Place salmon, skin-side down, on the prepared pan and spread the miso mixture on top. Halve the remaining lemon and lime and arrange around the salmon, cut-sides up.

Step 3

Broil the salmon just until it flakes with a fork, 7 to 12 minutes. Serve with the lemon and lime halves and sprinkle with scallions, if desired.