Preheat oven to 400°F with a rack set in the upper third of the oven.
Arrange fish on a parchment-lined baking sheet and season with salt and pepper. Drizzle with EVOO then halve the zested lemon and douse each filet with about 1 teaspoon juice from one of the lemon halves and brush each filet with a tablespoon of Dijon mustard.