Preheat the oven to 350°F. Line an eight-inch square cake pan with parchment paper and butter it lightly.
In a large bowl, soak the Kellogg's Two Scoops Raisin Bran in the milk for about 30 minutes. Stir occasionally.
Using an electric mixer, cream together the butter and sugar. Add the egg and lemon zest and mix until combined. Stir in the flour, baking powder and Kellogg's Two Scoops Raisin Bran mixture and mix again until combined. Spoon the batter into the prepared cake pan and bake in the centre of the oven until a toothpick inserted into the cake comes out clean. Remove cake from the oven and place it on a wire rack to cool.
Using an electric mixer, cream the butter, cream cheese, lemon zest and powdered sugar until smooth. Stir in the elderflower cordial and use the mixer to incorporate it into the batter.
Slice the cake horizontally into three even layers and fill with layers of the butter cream. Garnish with the edible gold and edible flowers.