Oil a 9" springform pan and line the bottom with parchment paper. Preheat oven to 350˚F.
Wash, pit then cut the fresh plums into thin slices; about 12 -16 slices per fruit. Set aside.
In a large bowl, whisk together 2 eggs with coconut sugar. Add Greek yogurt, oil, vanilla, lemon juice, lemon zest and combine.
In a small bowl, whisk together: flour, baking powder and salt until well incorporated.
Add flour mixture to the batter 1/3 at a time, letting the flour incorporate with each addition and continue mixing just until well combined.
Transfer the batter into the prepared pan and smooth the top. Arrange the plum slices over the cake batter in large circles, starting from the edges of the pan and working towards the centre of the cake.
Bake at 350˚F for 45-55 minutes, or until a toothpick inserted into center comes out clean. Let cake rest in pan 15-20 minutes before removing the ring.
Run a thin spatula around cake edges to loosen from pan, then transfer to a cake platter. Cool and dust with powdered sugar, if desired. Slice with a serrated knife.