Step 1: Preheat your oven to 180°C (350°F). Grease and flour a 9-inch round cake pan or a similar-sized square pan. Line the bottom with parchment paper.
Step 2: In a medium bowl, whisk together the semolina flour, all-purpose flour, baking powder, and salt. Set aside.
Step 3: In a large mixing bowl, cream together the softened butter and 1 cup of granulated sugar until light and fluffy (about 3-5 minutes).
Step 4: Add the eggs one at a time, beating well after each addition. Stir in the vanilla extract, orange zest, and 1 teaspoon of rose water.
Step 5: Gradually add the dry ingredient mixture to the wet ingredients, alternating with the milk and 1/4 cup of orange juice. Begin and end with the dry ingredients. Mix until just combined; do not overmix.
Step 6: Gently fold in the chopped pistachios, reserving a small amount for garnish.
Step 7: Pour the batter into the prepared cake pan and smooth the top. Bake for 35-45 minutes, or until a wooden skewer inserted into the center comes out clean and the cake is golden brown.
Step 8: While the cake bakes, prepare the syrup. In a small saucepan, combine 1/2 cup water, 1/2 cup sugar, and 1/4 cup orange juice. Bring to a simmer over medium heat, stirring until the sugar dissolves. Remove from heat and stir in the remaining 1 teaspoon of rose water. Let the syrup cool slightly.
Step 9: Once the cake is out of the oven, immediately prick the hot cake all over with a wooden skewer. Slowly and evenly pour the warm syrup over the entire surface of the cake. Let the cake absorb the syrup and cool completely in the pan before inverting onto a serving plate.
Step 10: Garnish the cooled cake with the reserved chopped pistachios and dried rose petals (optional) before serving. Slice and enjoy!