Preheat the oven to 450 F. Cover the bottom of a baking sheet with parchment paper. Place the salmon fillets on the baking sheet, skin side down.
In a small bowl, whisk together the mayonnaise, water, honey, Dijon mustard, ancho chili powder, garlic powder, salt and pepper to prepare the glaze.
Using a pastry brush, apply one-quarter of the prepared glaze evenly over the tops and sides of each salmon fillet. Place the baking sheet in the oven.
Cook until the very center of the thickest part of one of the fillets is still slightly underdone when cut with a paring knife, about 15 minutes. Sprinkle the sliced green onions over the fillets.