Heat the oven to 180C/fan 160C/gas 4. To make the syrup, scoop the pulp and seeds from the 4 passion fruits into a small pan, add the 2 tbsp caster sugar and 2 tbsp water and simmer until syrupy.
Butter 4 × 150ml metal pudding moulds. To make the puddings, scoop the pulp from 2 passion fruits then push through a sieve and discard the seeds that are left. Whizz the butter, 100g sugar and lemon zest in a food processor until pale and fluffy. Mix in the eggs one by one followed by the sieved passion fruit pulp. Add the flour and pulse until incorporated into a smooth mixture.
Divide between the moulds then sit them in a small roasting tin. Pour water from a kettle into the tray to come 1cm of the way up the moulds. Cover the whole tin with a sheet of foil and put in the oven.
Bake for 25-30 minutes, or until a skewer poked into the middle of the puddings comes out clean.
Turn out and spoon the syrup over the top. Serve with ice cream or cream.
To cook in the microwave, use 4 × 150ml plastic microwavable pudding moulds with lids. After filling with the pudding mix, cover with a lid and microwave on medium (650w-750w) for 4 minutes. Turn out and serve as above