1.Preheat the oven to 350°F and prepare an 8-inch round cake pan by greasing and lining it with parchment paper.
2.In a food processor, pulse the pistachios until finely ground. Be careful not to over-process, or it will turn into a paste.
3.Whisk together the ground pistachios, flour, baking powder, and salt in a large bowl.
4.Cream the butter and sugar in a separate bowl until light and fluffy. Beat the eggs one at a time, followed by the vanilla extract.
5.Add the dry ingredients in three additions, alternating with the Greek yogurt and milk, beginning and ending with the dry mixture. Mix until just combined.
6.Pour the batter into the prepared cake pan and smooth the top. Bake for 35-40 minutes, or until a toothpick inserted into the center comes clean.
7.Allow the cake to cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.
8.Serve the cake with your choice of toppings, such as whipped cream or a dusting of powdered sugar.