Step 1: Preheat your oven to 350°F (175°C) and grease a 9-inch round cake pan or line it with parchment paper.
Step 2: In a small bowl, crush the saffron threads and soak them in 1 tablespoon of warm orange juice for 15 minutes to release the color.
Step 3: Using a stand mixer or hand mixer, cream together the softened butter and sugar until the mixture is light and fluffy, about 3-5 minutes.
Step 4: Add the eggs one at a time, beating well after each addition. Mix in the orange zest and the soaked saffron liquid.
Step 5: In a separate bowl, whisk together the flour, ground pistachios, baking powder, and salt. Gradually fold the dry ingredients into the wet ingredients, alternating with the 1/4 cup of orange juice.
Step 6: Pour the batter into the prepared pan and smooth the top. Bake for 40-45 minutes, or until a skewer inserted into the center comes out clean.
Step 7: While the cake is baking, prepare the syrup by combining sugar, orange juice, saffron, and lemon juice in a small saucepan. Bring to a boil, then simmer for 5 minutes until slightly thickened.
Step 8: Remove the cake from the oven. While still hot, poke holes across the surface with a skewer and pour the warm syrup evenly over the cake. Allow it to cool completely in the pan before serving.