Preheat oven to 190 degrees C. Grease a 25cm cake pan and line the bottom with a round piece of baking paper.
In a large bowl whisk together 1 1/2 cups flour, bicarb soda, salt and cinnamon. In a separate bowl beat butter, brown sugar and white sugar with an electric mixer until light and fluffy; beat in eggs one at a time, then beat in vanilla essence and lemon zest.
Mix the butter mixture into the flour mixture, alternating with yoghurt until the mixture forms a smooth even batter. Spread the batter into the prepared cake pan. Place the plum slices into a bowl and toss with 2 tablespoons of flour. Arrange the plum slices onto the cake in a decorative pattern.
Bake in the preheated oven until browned, about 30 minutes. Loosely cover the cake with foil and bake until a toothpick inserted into the centre of the cake comes out clean and the cake pulls away from the sides of the pan, 30 to 40 more minutes.
Let cake cool completely in pan. Run a knife around the edge of the cake to loosen and remove from pan. Dust with powdered sugar before slicing.