Butter 4 × 150ml plastic pudding moulds. Whizz the butter, sugar and lemon zest in a food processor until pale and fluffy. Mix in the eggs one by one. Add the flour and pulse until incorporated. Divide between the moulds then cover with a lid or clingfilm and microwave on medium (650w) for 4 minutes. Heat the lemon curd with a squeeze of lemon juice in a small pan. Spoon over the top and serve.