01 -
Set your oven to 175°C (350°F) and let it warm up.
02 -
Rub butter all over a 10-inch pan, then sprinkle some flour on it.
03 -
Toss the flour, salt, and baking powder together in a medium-sized bowl.
04 -
Using the bowl of your stand mixer fitted with a paddle, beat butter and sugar until airy and pale. Stop once in the middle to scrape down the sides.
05 -
Add eggs one by one, beating each time so it mixes in smoothly.
06 -
Stir in vanilla and orange zest until it’s all blended.
07 -
Gently mix the dry ingredients into the wet ones with a wide spatula, just until combined.
08 -
Pour the batter into the buttered pan, spread the plums evenly on top, and bake for about 1 hour at 175°C (350°F) or until a clean skewer comes out clean from the center.