FOR THE CAKE:
8 ounces butter
1 cup plus 1 tablespoon sugar
3 large eggs
1 cup finely ground unsalted pistachios
1 cup finely ground blanched almonds
Juice and finely grated zest of 1 orange
½ cup plus 1 tablespoon all-purpose flour
FOR THE ICING:
1 cup confectioners' sugar
2 tablespoons lemon juice
Preheat oven to 350 degrees. Line the bottom of an 8-inch nonstick cake pan with parchment paper.
In a mixer fitted with a paddle, cream together the butter and sugar until light and fluffy. Add the eggs one at a time, then add the ground pistachios and almonds.
Add the orange juice, orange zest and mix well. Using a rubber spatula, fold in the flour; do not overmix.
Scoop the mixture into the cake pan, and bake until the top is firm and a light golden brown, about 40 minutes. Lightly cover the top of the cake with foil and continue baking until a toothpick inserted into the center comes out dry, about 10 minutes.
Allow the cake to cool in the pan for several minutes, then remove and cool on a rack.
When the cake is cool, make the icing: mix the confectioners' sugar and lemon juice together in a small bowl, and pour over the cake.
Allow the icing to set for 30 minutes before serving.