Preheat the oven to 180ºC/350ºF/gas 4. Generously grease a 2-litre bundt tin with butter.
Place the sugar, flour, baking powder, butter, yoghurt and tahini into a food processor. Crack in the eggs, squeeze in all the citrus juice and blitz until smooth.
Pour the mixture into the bundt tin, scraping it out of the processor with a spatula, then give the tin a jiggle to level out the mixture. Bake for 50 to 55 minutes, or until golden and an inserted skewer comes out clean.
Leave the cake to cool in the tin for 5 minutes, then turn out onto a wire rack and leave to cool completely.
To make the amazing drizzle, halve the pomegranate and squeeze 30ml of juice through a sieve into a jug, then squeeze in 30ml of lime juice. Pour into a bowl with the rosewater, then stir in the icing sugar to give you a thick drizzling consistency.
Smash up the pistachios in a pestle and mortar into a mix of random small chunks and lovely dust.
Pour the drizzle over the cooled cake, letting it drip down the sides. Slice, and serve with a sprinkling of pistachio dust.