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. 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 1/2 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.