Preheat the oven to 350 F.
Grease and line a 9-inch springform pan with parchment paper, or you can also make this in a 9-by-9-inch baking dish.
Cream together vegan butter/butter and sugar until light and fluffy, about 3-4 minutes, using either a handheld mixer or stand mixer with the paddle attachment.
Add the honey to the sugar mixture and mix until well incorporated.
Add the eggs, vanilla and freshly grated ginger, and mix until they are also well incorporated.
Sift together the flour, baking powder, salt and cardamom. Slowly add the dry ingredients to the wet ingredients, and mix until just incorporated. Be careful not to over-mix.
Pour the batter into the lined and greased cake pan. Add the sliced plums on top of the cake; they will sink as they bake. Top the cake with a generous sprinkling of Turbinado/raw sugar, or regular sugar if you don’t have raw sugar.
Bake 35-40 minutes, or until a cake tester comes out clean when tested in the center of the cake.
If desired, you can brush honey on top of the cake once it has cooled: Heat ¼ cup of honey until just warm, and then brush it over the cake.
Serve topped with whipped cream or ice cream. Can be made a day in advance.