Preheat oven to 350°F (177°C). Grease the interior of an 8 inch round springform pan and then line the inner sides and bottom with parchment paper. You do need to use parchment paper because even if you use a well greased nonstick pan, the cake will stick to the cake pan.

In a large mixing bowl, add eggs and sugar. Beat on highest speed for about 10 minutes or until mixture becomes very thick and turns a very pale yellow, and becomes at least quadruple in volume. When the eggs are ready, the mixture should be thick enough that it seems like soft peaks are going to form (when the beater pushes through, it leaves indents/lines that don't disappear right away). However, once you stop beating, the mixture will immediately deflate. This is normal. See photo in post for reference.

Using a spatula, gently fold in ⅓ of the pistachio flour. Repeat with another ⅓ of the flour and then the final ⅓. Try your best not to deflate the egg mixture too much. When you are done, the pistachio flour should be all evenly incorporated but the mixture should still look like an egg batter.

Transfer your batter to your prepared cake pan. Smooth the surface with your spatula.

Bake cake for about 35-45 minutes (mine was done at 40 minutes). The surface of the cake should be light brown and feel lightly firm.

Let cake cool for about 1 hour and then gently release it from the cake pan. The cake is easier to cut and tastes best after it is fully cooled, so I recommend waiting a few more hours (or until the next day) to serve it.

If desired, you can dust the cake with powdered sugar before serving.

When slicing the cake, use a large sharp knife and cut into it gently. The surface of the cake will break as you cut it (it has a delicate, meringue-like surface). If you cut into the cake with too much force, you will squish the cake crumb and cause the cake to sink in too much.

Uneaten cake can be stored for about 1-2 days at room temperature and longer in the fridge or freezer.