Butter a 1-litre baking dish, and dollop the syrup
in the bottom. Put the butter and sugar in a food
processor and blitz until pale. Beat in the eggs one
by one, then the vanilla. Add the flour and pulse until
just mixed. Scrape into the dish, on top of the syrup.
Either cover with cling film and microwave on
medium for 7 1/2 minutes or bake in the oven at
180C/fan 160C/gas 4 oven for 30 minutes until risen
and golden. Serve with lashings of custard.