Serve 4

1. Stir the port and ½ of the honey in a saucepan with the lemon juice and bring to a boil. Lower the heat and add the plums and cook for 4 minutes, until the plums are soft but not falling apart. Using a slotted spoon remove the plums and set aside to cool.
    
2. Line a spring-form pan with parchment and put the pan on a baking sheet. Preheat oven to 350F.
    
3. Blend all the dry ingredients together and set aside.
    
4. Raise the heat on the poaching liquid and reduce it down for another 10 minutes, until slightly thickened.
    
5. In the bowl of a mixer, rub the lemon zest into the sugar until moist and crumbly looking. Add the butter and beat until creamy and fluffy.
    
6. Add the eggs one at a time, and then add the remaining honey and the vanilla.
    
7. On reduced speed add the dry ingredients until just blended and smooth, then scrape batter into the spring-form pan.  Scatter the plums on top.
    
8. Bake at 350F until the middle is puffy and slightly brown, around 55 minutes, and a knife into the centre comes out clean.