01 -
Preheat the oven to 175°C (350°F).
02 -
Grease a 10-inch cake pan with butter and dust with flour.
03 -
In a medium bowl, whisk together the flour, baking powder and salt.
04 -
In the bowl of a stand mixer with the paddle attachment, cream together the butter and sugar until light and fluffy, about 5 minutes. Scrape the bowl halfway through.
05 -
Add the eggs, one at a time, beating well after each addition.
06 -
Add the orange zest and vanilla extract and stir to combine.
07 -
Using a wide rubber spatula, gently fold in the dry ingredients until combined.
08 -
Transfer the batter to the prepared cake pan and top with the plum slices. Bake at 175°C (350°F) for about 1 hour, or until a skewer inserted in the center of the cake comes out clean.