Grease a 1-litre microwave-proof glass dish with the oil.
Put the butter in a mixing bowl with the sugar, flour, eggs, lemon juice and most of the zest. Using an electric hand-held whisk, beat until light and fluffy.
Spoon the mixture into the prepared glass dish. Cover with clingfilm, pierce a few times, then microwave on low for 9 minutes. Turn out onto a serving plate.
Put the lemon curd in a small microwave-proof bowl and warm on high for 30 seconds until melted. Drizzle over the pudding, then decorate with the reserved lemon zest. Serve immediately with a dollop of crème fraîche