Special equipment: This extraordinary cake can be scattered with rose petals to make it even more special. It's extremely feminine and is therefore perfect for Mother's Day or for sharing with girlfriends for a birthday or hen night. It's very moist so it keeps extremely well in the refrigerator for a few days.
Preheat the oven to 350 degrees F. Line the base and sides of an 8 1/2-inch springform pan with greaseproof or parchment paper.
Sift the flour, baking powder, and salt into a large bowl. Add the ground almonds and sugar, and mix.
In a medium-sized bowl, mix together the eggs, honey, yogurt, sunflower oil, and lime zest. Make a well in the center of the dry ingredients, and slowly pour in the wet ingredients, bringing the ingredients together with a whisk until they are just combined. Add some chopped pistachios to the mixture if you wish, or reserve for decorating, if using. Pour the batter into the prepared pan, and bake until a skewer inserted into the center of the cake comes out clean, about 50 minutes. Allow the cake to cool in the pan for about 20 minutes.
To make the syrup: In a small saucepan, boil half a cup water and the sugar until reduced by half, about 5 minutes. Add the lime juice, and boil for another 2 minutes, then cool, and add rosewater to taste. With a fine skewer, poke holes on top of the warm cake and, with a tablespoon, spoon the syrup all over the top. Scatter the pistachios over, if using, and let sit for 1 hour. Decorate with rose petals, if using. Serve with cream, yogurt, sliced mangos or berries.