Preheat oven to 325°F (160°C) and place racks in the center of the oven.

Line baking sheets with parchment paper.

Combine rapadura sugar, salt, espresso powder, and toasted hazelnuts in a food processor.

Process until the mixture is finely ground.

Transfer the nut mixture to a mixing bowl.

In a separate bowl, beat egg whites until stiff peaks form.

Gently fold the nut mixture into the beaten egg whites.

Add vanilla extract and orange zest to the batter.

Mix until all ingredients are well blended.

Spoon the batter onto the prepared baking sheets, leaving space between each cookie.

Bake in the preheated oven for 25 minutes, or until the cookies are golden brown on top.