Preheat oven to 350F (180C).
Grease bottom and sides of a 9-inch springform pan/or round cake pan with butter. Line bottom and sides with parchment paper. Set aside.
Place 1 cup pistachios and cardamom powder in a high speed blender/food processor and blitz until finely ground. Transfer to a large mixing bowl. Add ground almonds, semolina, baking powder and salt. Mix together and set aside.
Using an electric mixer, cream butter and sugar until fluffy, in another bowl. Slowly add eggs 1 at a time and continue to mix until smooth and fully incorporated.
Using a spatula, fold the dry ingredients into the butter mixture, being careful not to over mix. Fold in lemon zest, lemon juice, rosewater and vanilla extract. Scrape batter into greased pan and level with spatula.
Bake for 55 to 60 minutes, or until a wooden skewer inserted into centre of cake comes out clean but oily. Let rest for 10 minutes before removing from pan.
To serve, drizzle warm rose syrup all over cake. Drizzle cake with glaze. Chop remaining pistachios and sprinkle all over cake along with dried rose petals.
Cake can be refrigerated for upto a week. Before serving, simply warm up cake, or let stand at room temperature for a bit.