Heat 1/2 cup of the cream with the saffron to a simmer, then remove from heat and allow to cool 20 minutes. Then chill in the fridge.
CANDIED ROSE PETALS.
Remove the petals from the two roses. Whip the egg whites until they are foamy, then brush them onto both sides of the petals with a pastry brush. Sprinkle generously with the sugar. Place them on a wire rack to cure for 6 hours, then store them in the fridge after that if you aren't using them the same day.
Set the oven to 325°F Generously butter an 8" springform pan.
In a medium bowl whisk together the cake flour, 7 tbsp of the powdered sugar, baking powder, and salt.
In a small bowl beat the egg yolks, water, oil, lemon zest, and cardamom until combined.
In another small bowl whip the egg whites until soft peaks form. Slowly add the other 7 tbsp of the powdered sugar and continue whipping until it resembles marshmallow fluff.
Add the egg yolk mixture to the flour mixture and whisk gently to combine, eliminating any lumps. Then fold in the egg white mixture with a spatula in 3 batches, gently stirring just enough to combine into a uniform mixture.
Pour into springform pan, smooth with the spatula, and bake 30-35 minutes, or until top is golden brown and a cake tester comes out clean.
Remove from oven and allow to cool in springform pan, then gently loosen the sides with a butterknife (if necessary) and remove the sides of the pan. Gently loosen from the bottom with the knife and remove the bottom of the pan. Place onto a plate or cake decorating platter. Allow to cool COMPLETELY before frosting.
WHIPPED CREAM TOPPING.
Whip the unused 1.5 cups cream together with the powdered sugar and rosewater until soft peaks form. Strain in the saffron infused cream (use a spatula to push through all the cream you can get without breaking the saffron threads). Continue to whip until stiffer peaks form. With the addition of rosewater the peaks will not be as stiff as traditional whipped cream.
Cut the cake in half at the midway point to form 2 layers. Trim off the top if it is uneven.
Remove the top half of the cake and place a layer of the whipped cream on top of the lower half of the cake. Then place the top half of the cake back on and cover the top and sides of the cake with the whipped cream. Use a cake decorating spatula to smooth the whipped cream.
Sprinkle chopped pistachios on top of the cake and decorate the top with the candied rose petals.