Place fish on a large plate or another rimmed baking sheet, brush with egg white mixture, and sprinkle with 2 Tbsp. sesame seeds, patting gently to adhere. Turn over and repeat on opposite side, with egg white and another 2 Tbsp. sesame seeds. Transfer fish to preheated baking sheet, drizzle with 1 Tbsp. oil, and season with more salt. Bake until mostly cooked through and the tip of a paring knife easily slides through flesh, 20–25 minutes.