Preheat oven to 350°F (175°C). Grease a 9” (23 cm) round cake pan.
In a medium bowl, whisk together the flour, sugar, baking powder, and cinnamon.
In a small bowl, whisk together the milk, melted butter, and vanilla extract. Pour the wet ingredients into the dry ingredients and stir until just combined.
Spread the batter into the prepared pan. In a small bowl, mix together the apples, plums, sugar, and cinnamon. Sprinkle the mixture over the batter.
Drizzle the melted butter over the top. Bake for 25-30 minutes, or until a toothpick inserted into the center comes out clean.
Let cool in the pan for 10 minutes before removing and serving.
Interesting Facts
Cinnamon Swirls have been a popular dessert in Europe since the Middle Ages.
The combination of apples, plums, and cinnamon is known as a “fruit compote” in France.
The swirl pattern is created by the melted butter dripping down the sides of the cake.