Step 1: Preheat your oven to 350°F (175°C) and grease a 9-inch springform pan.
Step 2: In a medium bowl, combine the crushed pistachios, 3 tbsp melted butter, and brown sugar. Press firmly into the bottom of the prepared pan to form the crust.
Step 3: Place chopped dates in a bowl and pour 1 cup of boiling water over them. Let them soak for 10-15 minutes, then mash into a paste or blend for a smoother texture.
Step 4: In a separate bowl, whisk together the flour, baking soda, ground cardamom, and salt.
Step 5: In a large mixing bowl, cream the softened butter and sugar together until light and fluffy. Beat in the eggs one at a time, then stir in the orange zest and orange juice.
Step 6: Gradually add the dry ingredients to the wet ingredients, alternating with the date paste, and mix until just combined.
Step 7: Pour the batter over the pistachio crust in the pan and smooth the top.
Step 8: Bake for 40-45 minutes, or until a toothpick inserted into the center comes out clean.
Step 9: Allow the orange cardamom date cake with pistachio crust to cool in the pan for 15 minutes before removing the sides and slicing.