For the Cake:

1. Preheat the oven to 350°F. Liberally spray a 9-inch springform pan (see Notes) with nonstick spray.
2. Place the pistachios in a food processor and pulse until they are finely ground – be careful not to go too far or you’ll end up with pistachio butter.
3. In a large mixing bowl, whisk together the oil, eggs, vanilla, lemon zest and juice, and buttermilk. Whisk in the sugar.
4. Measure out 1 cup of the ground pistachios and add to a second bowl (reserve the rest for serving). Whisk in the flour, baking powder, and salt.
5. Fold the dry ingredients into the wet ingredients, stirring until everything is just combined. Resist the urge to overmix (this results in a dry, dense cake).
6. Pour the batter into the prepared pan. Bake for 40-50 minutes or until golden brown around the edges and set in the middle (insert a toothpick in the center and if it comes out mostly clean with a few moist crumbs, the cake is done).
7. Allow the cake to cool completely in the pan and then carefully run a knife around the edges and release the springform sides. Transfer to a serving plate.

For Serving:

1. Whisk together the lemon juice and zest and powdered sugar until a thick but pourable glaze forms.
2. Pour the glaze over the cake, as liberally as you want.
3. Garnish with chopped pistachios, lemon slices, and fresh berries – all optional!
4. Slice and serve!