Preheat the oven to 375 degrees. Spray two mini muffin tins (24 muffin cups per pan) with cooking spray.
Beat the egg whites until foamy, starting on low speed and gradually increasing to high. Gradually add ¼ cup sugar and beat until stiff peaks form.
In another mixing bowl, combine the egg yolks, the rest of the sugar, the orange zest, and salt. Beat on medium-high until thick and smooth, about 2 minutes. Stir in the almond flour. Stir in a large spoonful of the egg whites into the yolk mixture then fold in the rest gently. Divide the mixture evenly among the prepared muffin tins and bake for 10 minutes or until a toothpick inserted into the center comes out clean and they are lightly golden brown. Let cool in the pan for 5 minutes then transfer to a wire cooling rack to finish cooling.