Heat the oven to 180℃/160℃ Fan/350°F. Butter an ovenproof dish (mine measures 26 x 17 x 5cm / 10 x 7 x 2 inches, though any ovenproof dish of the same depth, with a 1.5 litre / 6-cup capacity would be fine).Put the butter, sugar, rice flour, ground almonds, Greek yogurt, salt, baking powder and eggs into a processor. Finely grate over the zest of the lemon and blitz until you have a thick batter. Pour the 2 tablespoons of elderflower cordial through the funnel of the processor, with the motor still going, until combined.If you don't have a processor, cream the butter, sugar and lemon zest together until smooth, light and aerated. In another bowl, mix the flour, ground almonds and salt together, add just 1 teaspoon of baking powder; you don't need as much for the non-processor variant, as you're whipping more air into the batter. Beat 1 egg into the butter mixture, and when that's combined, beat in a third of your dry ingredients, and carry on in like manner until eggs and dry ingredients are used up. Finally, beat in the Greek yogurt and the 2 tablespoons of elderflower cordial.Pour and scrape this fragrant, slightly nubbly and quite delicious batter into your prepared dish and bake for approx. 25 minutes, covering loosely with foil at 20 if the top is browning too much.While the pudding cake is in the oven, prepare the drizzle. Mix 3 tablespoons of juice from the zested lemon and 100ml / 7 tablespoons of elderflower cordial in a jug.When the pudding cake is out of the oven, prick the sponge and drizzle with the elderflower lemon syrup. Eat warm with double cream. This is an order!