These plum cakes are simply to die for!
For plum cakes, preheat oven to 350°F.
Cream butter with sugar and 2 Tbsp brown sugar until fluffy.
Beat in eggs, orange zest and vanilla. Stir in buttermilk.
In a separate bowl, sift together flour, baking soda and salt. Add flour to butter mixture and incorporate.
Spoon batter into greased ramekins. Arrange 3 plum wedges onto cake surface and press gently, so as not to press plum all the way to the bottom of the ramekin.
Sprinkle tops of plums with 3 Tbsp brown sugar and bake for 15 to 20 minutes, until cake is golden brown around the plum. Cool for 10 minutes.
For crème fraîche, stir together cream and buttermilk, place in a plastic cup or bowl and cover with plastic wrap.
Immerse cup or bowl in hot water, up to the level of the cream and store in a warm place (near oven, radiator) for 24 to 48 hours. You will know when it’s ready because you will see the thin-textured whey settled at the bottom. Chill before using, being sure not to stir whey (the liquid that settles at the bottom) into crème fraîche (it will thin it out). Yield: 1/2 cup crème fraîche.
Before serving, stir crème fraîche with remaining 1 Tbsp brown sugar. Serve plum cakes warm or at room temperature with a dollop of crème fraîche.