• Preheat the oven to 350°F (180°C). Brush a 12-cup Bundt pan with soft butter, making sure to cover every angle and surface, then coat it with flour. Tap the pan over the sink to remove any excess flour.
• Sift together the all-purpose flour, potato starch, and baking powder in a bowl. Whisk to combine and set aside.
• In a medium bowl, combine the orange zest, freshly squeezed orange juice, and 20 ml of vodka. Set aside.
• Separate the egg whites from the egg yolks.
• Using a handheld or stand mixer, beat the egg yolks and sugar on high speed until pale and fluffy, about 5 minutes. With the mixer on low speed, add the sifted flour, potato starch, and baking powder. Scrape down the sides and bottom of the bowl with a rubber spatula as needed.

  Add the orange juice, orange zest, and vodka. Mix on low speed until incorporated.
• Add the melted butter and mix on low speed until combined.
• Take a clean medium-sized bowl and combine the egg whites and salt. Using an electric mixer, beat until stiff but not dry.
• Add the egg whites to the batter mixture. Using a rubber spatula, gently fold the egg whites into the batter until just combined. Do not overmix.
• Pour the batter into the prepared Bundt pan, spreading it evenly. Place the Bundt pan on the middle rack of the oven.
• Bake for about 50 minutes, or until lightly golden and a toothpick inserted into the center comes out clean.

  Cool the cake in the pan on a wire rack for 15 minutes, then carefully invert it onto a rack and allow the cake to cool completely before glazing.

Make the lemon glaze:

• In a small saucepan, warm the lemon juice. In a small bowl, whisk the confectioners' sugar and warm lemon juice together until smooth and shiny. The consistency should be pourable. If it's too thick, add 1 tablespoon of lemon juice to thin it out, or more powdered sugar to thicken it.
• Place the cooled cake on a wire rack with parchment paper underneath, or on a smooth surface like the kitchen counter.
• Pour the lemon glaze over the cooled Bundt cake and let it drip down the sides. Decorate with chopped pistachios and enjoy!