Grease a 9-inch bundt pan generously with butter or margarine. (You’ll thank yourself later when the cake slides right out.) Preheat your oven to 350°F (175°C).
In a large bowl, beat the sugar and eggs, adding one egg at a time. Once combined, add the softened butter and mix for about 3 minutes until light and creamy. (This is the part where you pretend you’re on a baking show.)
In a separate bowl, mix the baking powder with the flour. Soak the pistachios and hazelnuts in water for a minute—this keeps them from sinking to the bottom of the cake. Drain and toss them into the flour mixture. (Reserve about 2 tablespoons of pistachios for garnish.)
Slowly fold the dry ingredients into the wet mixture. Stir until fully incorporated, but don’t overmix—we want a tender cake, not a dense brick. Pour the batter into your prepared bundt pan and smooth out the top. Bake for about 40 minutes, or until a toothpick inserted into the center comes out clean.
Resist the urge to dig in right away! Let the cake cool in the pan for about 10 minutes before transferring it to a wire rack to cool completely.
