Brush 9 sections of a 12-section muffin tray, preferably non-stick, lightly with oil. Mix together the polenta, sugar, baking powder and ground almonds in a bowl.
Whisk together the almond extract, soured cream, oil, lemon rind and eggs in a separate bowl until combined. Add to the dry ingredients and mix to a thick paste.
Divide the cake mixture between the tin sections and arrange a couple of plum wedges on top of each.
Bake in a preheated oven, 180°C (350°F), Gas Mark 4, for 20–25 minutes or until risen and beginning to colour around the edges.
Leave in the tin for 5 minutes, then loosen the edges with a knife and transfer to a wire rack.
Pierce the tops of the cakes with a skewer. Mix together the lemon juice and honey and drizzle over the cakes while still warm.