Divide the plums in two and pit them. In a frying-pan, roast the plums in butter, honey and thyme for 5 to 8 minutes.
Separate egg whites and egg yolks.
Beat the soft butter and half of the sugar then add the yolks.
Assemble the flour and baking powder, then incorporate to the mix.
Beat the egg whites with a pinch of salt until stiff then, while still beating, add the leftover sugar.
Vigorously incorporate half the stiff egg white peaks. Do the same with the other half but this time very softly, very carefully.
Pour the batter into a buttered and floured springform pan. Place on top the plums with their cooking juice. Cook for 35 minutes in hot oven (at 180°C or 350°F).
