Preheat the oven to 325ºF and grease an 8-inch round cake pan. Line the bottom with a circle of parchment and grease the parchment.

In a food processor or chopper, chop the nuts until mostly finely ground with some larger pieces. Reserve about 2 tablespoons for the top of the cake.

In a large bowl, beat together the eggs and sweetener until lightened and frothy, about 1 minute. Beat in the oil, whipping cream, and vanilla extract.

Add the almond flour, ground pistachios, protein powder, baking powder, and salt and beat until well combined.

Pour the batter into the prepared baking pan and bake 40 to 50 minutes, until golden brown and just firm to the touch. Remove and let cool 20 minutes in the pan, then run a sharp knife around the sides and flip out onto a cake plate.

Dust the top with powdered sweetener and sprinkle with the reserved pistachios.