Preheat oven to 350 degrees.
Prepare an 8-9" cast iron skillet, or an 8 - 9" square baking pan by greasing with butter. Then add the sugar to the pan and shake the sugar all over to pan. Remove any excess.
Place pitted and cut up plums in the bottom of the prepared pan and set aside.
In a bowl combine the eggs, sugar, milk, almond extract, vanilla, flour and salt and whisk until completely combined. I find the whole wheat flour to be hard to mix in completely sometimes so I use an immersion blender to make it easier. If you don't have one, just keep whisking, it will work! Once mixed, pour into the pan and place in the oven.
Bake for 55-60 minutes until just golden brown on top and completely set. Let cool and serve with a sprinkle of powdered sugar and a dollop of sweet whipped cream and some sliced almonds if desired. Enjoy!