Preheat your oven to 175°C (350°F) to ensure even baking.
Line a 9-inch round baking pan with parchment paper and grease the sides with butter for easy removal.
In a large bowl, whisk together ground pistachios, ground almonds, flour, and baking soda until well blended.
In another bowl, beat 200g butter and 175g sugar until light and fluffy to incorporate air into the batter.
Add eggs one at a time, mixing well after each addition, then stir in lemon zest and vanilla essence until combined.
Gradually add the dry mixture to the wet ingredients, mixing until just combined to avoid a dense cake.
Pour batter into the prepared pan and smooth the top with a spatula. Bake for 25-30 minutes until a toothpick comes out clean.
Remove the cake from oven and cool in the pan for 10 minutes, then transfer to a cooling rack to cool completely.