Preheat the oven to 350 °F. Lightly spray a 9-inch cake pan with nonstick spray.
Stir together 1½ tablespoons white granulated sugar and ¼ teaspoon cinnamon in a small bowl. Set aside for later.
In a medium bowl, whisk together the dry ingredients: 1 cup of flour, ½ teaspoon cinnamon and ¼ teaspoon nutmeg.
In another bowl, use an egg beater to mix the egg, egg whites and brown sugar until pale yellow and foamy. Beat in the milk, vanilla extract and almond extract.
Mix the flour mixture into the egg/milk mixture.
Mix the sliced plums with an extra tablespoon of flour, just to let a light coating (this will prevent the fruit sinking to the bottom) Then, stir the sliced plums into the mixture.
Pour into the prepared cake pan and sprinkle with the sliced almonds and reserved cinnamon/sugar mixture.
Bake for about 45 to 50 minutes, until a skewer or knife inserted into the middle of the cake comes out clean.