Preheat oven 425 degrees. In a small saucepan, whisk together miso, brown sugar, vinegar and water. Bring to a boil and reduce to a simmer for 1-2 minutes or until the brown sugar has melted.

Place fish filets on a sheet pan lined with parchment paper. Season with salt and pepper. Brush evenly with miso mixture. Bake in the oven for 10 minutes. Turn the heat to broil and cook until top has slightly blackened, and fish is cooked through, about 5 minutes. Be careful not to burn.

While the fish is cooking, make the noodles. Using the spaghetti blade on the spiralizer, cut zucchini into spaghetti. If you do not have a spiralizer, you can just cut zucchini into thin slices.

Use a paper towel to squeeze the zucchini of all excess moisture. Heat a medium skillet to a medium-high heat. Add sesame oil, garlic and ginger. Cook for 1-2 minutes or until softened. Add in zucchini noodles, and cook until wilted, about 2-3 minutes. Season with salt and pepper.

Serve noodles with fish. Garnish with sliced green onion.