First, you need to make the sauce, whisk together the cornstarch with the water. Then add all the remaining ingredients and give it another whisk.
Using a pot, bring the sauce to a boil and let simmer for 3-4 minutes. Reserve and let cool.
Pre-heat oven to 400F. Cut your salmon filet. Cover a pan with parchment paper or foil and lay your filet on it. Using a spoon pour some of the sauce on the salmon. You don’t want to make a sauce bath here but make sure the top and each side are covered.
Put some foil on top of the pan ( this will prevent too much browning). Cook for 15 minutes. Remove foil and cook for another 5 minutes.
Optionally you can lightly brush some more sauce on top of the salmon just before serving.