Preheat the oven to 160C/140C Fan/Gas 3. Grease a 23cm loose-based cake tin and line with baking paper.
Sift the flours together. Beat the butter and sugar together in a bowl until soft and creamy.
Beat in the eggs, one at a time, adding 1tbsp flour with the last two. Fold in the rest of the flour, plus the orange zest and juice. Transfer to the tin, level the top and bake for 50 minutes or until the middle springs back when pressed and a skewer inserted in the middle comes out clean. Cool on a wire rack.
Melt the jam in a pan, then push through a sieve to remove lumps. Put a plate upside down on top of the cake, then flip it over. Brush the top and sides with jam.
Add red and yellow colouring to the icing to make orange, kneading it together until you have an even colour. Roll out on a surface dusted with icing sugar to make a 29cm round.
Using the rolling pin to support it, carefully lift the icing and drape it over the cake. Dust your hands with icing sugar and smooth the icing in place, massaging the sides with dusted hands.
Draw a web on top with piping icing and place a scary spider in the web.