01 - Preheat oven to 340°F (170°C). Butter and line an 8-inch (20 cm) round cake tin.
02 - In a large mixing bowl, cream the softened butter with caster sugar until pale and fluffy using a whisk or mixer.
03 - Add eggs one at a time, beating well after each addition to ensure a smooth mixture.
04 - Stir in Greek yogurt, lemon zest, and rosewater until combined.
05 - In a separate bowl, whisk together ground almonds, all-purpose flour, ground cardamom, baking powder, and salt.
06 - Gently fold dry ingredients into the wet mixture until just incorporated; do not overmix.
07 - Pour batter into prepared tin and smooth the top with a spatula.
08 - Bake for 40 to 45 minutes, or until a skewer inserted in the center comes out clean.
09 - Allow cake to cool in tin for 10 minutes, then transfer to a wire rack to cool completely.
10 - In a small bowl, mix icing sugar with enough rosewater to form a thick, pourable icing.
11 - Drizzle icing over cooled cake. Sprinkle chopped pistachios and optional dried rose petals on top.