Preheat the oven to 350°F (175°C). Grease and flour a 9-inch round cake pan.
In a large mixing bowl, whisk together the flour, sugar, baking powder, baking soda, and salt.
In another bowl, combine the ricotta cheese, softened butter, eggs, vanilla extract, orange zest, and orange juice. Mix until smooth and well combined.
Gradually add the wet ingredients to the dry ingredients, stirring until just combined. Fold in the chopped pistachios.
Pour the batter into the prepared cake pan and smooth the top with a spatula.
Bake for 30-35 minutes, or until a toothpick inserted in the center comes out clean.
Allow the cake to cool in the pan for 10 minutes, then transfer to a wire rack to cool completely. Dust with powdered sugar before serving, if desired.