Season both sides of the salmon with salt and pepper. Preheat the oven to 350 degrees. Lightly oil the inside of a pan or casserole dish that will fit your salmon fillet. Place the salmon in the dish skin side down and place in the oven for four to five minutes until the fish is just starting to cook by turning white on the edges. Remove the pan from the oven and turn the broiler to high.
While the broiler is heating, place the miso, soy sauce, garlic and ginger into a sauce or saute pan and simmer over medium heat until the sauce is slightly thicker than maple syrup. Taste and season with more soy (if it needs salt), sugar (if it's too acidic or salty) and water (if it's too thick or sweet), as needed, turn off and reserve.
Once the broiler has had time to warm up, place the salmon directly under the broiler for three to five minutes until some brown just starts to form on the top. Remove the salmon from the broiler three or four times and brush with glaze, each time placing it back under the broiler until the glaze starts to brown and sticks to the salmon.
Cook the salmon until the ends are slightly firm to the touch, and the center has a slight give.
Remove from the broiler and pour the remaining glaze over the salmon. You can serve from the dish or carefully transfer to a serving tray with two spatulas and serve.