Preheat the oven to 180C/160C Fan/Gas 4. Line a 12-hole muffin tray with cupcake cases. Beat 125g of the butter in a large bowl until creamy. Sift in a flour and baking powder, then add the caster sugar and eggs. Beat until evenly mixed.
Add enough red colouring to make the mixture very pale pink - like a brain. Stir in the cherries (to look like specks of blood). Divide the mixture between the cake cases and bake for 20 minutes or until the tops spring back when lightly pressed. Cool on a wire rack.
Beat the rest of the butter until creamy and gradually beat in the icing sugar. Add the milk and vanilla extract. Colour the mixture a very pale greyish-pink with red and black colouring.
Put the butter icing in a piping bag and snip off the end (or use a small freezer bag and snip off a corner). Pipe onto each cake in a wavy, s-shape pattern in two halves to make a brain.
Put the jam in another piping bag or freezer bag and pipe into the gaps.