Blend chopped lemon and sugar in a blender until smooth
Add eggs, oil, pistachios, and rose water to the blender and blend briefly for about 10 seconds so pistachios stay chunky
Add flour and baking powder if needed, then pulse only twice to avoid over-mixing and finish folding with a spatula if needed
Pour batter into a greased loaf or cake pan and bake at 350°F (175°C) for approximately 45 minutes until a toothpick comes out clean
Mix powdered sugar with lemon juice and rose water to desired consistency to make the icing
Drizzle icing over cooled cake and garnish with crushed pistachios and dried rose buds
