1 cup (240 milliliters) whole hazelnuts, peeled and toasted
1 cup (240 milliliters) whole pistachios, toasted
Line the bottom of a rectangular baking dish with parchment paper, then mist with cooking spray. Heat honey and sugar in a saucepan over medium heat, fitted with a candy thermometer, stirring periodically.
Meanwhile, whip egg whites with vanilla until stiff peaks form.
When sugar mixture reaches 300 F (150 C), remove from heat. Temper the egg whites by drizzling in about 1/4 cup (60 milliliters) of the hot sugar mixture while whipping. Continue adding hot sugar mixture to the egg whites while beating briskly until thick and shiny (six to eight minutes). Add salt and beat to combine.
Add lemon zest, toasted almonds, hazelnuts, and pistachios to nougat and fold until thoroughly combined. Pour nougat mixture into prepared baking dish and press with offset spatula to level. Mist the top of the nougat with cooking spray and layer with another sheet of parchment paper. Place a heavy object on top of the baking dish to weigh down the nougat. Set aside to settle for at least one hour at room temperature.
Slice with an extra sharp knife when ready to serve.