Preheat your oven to 350°F (175°C). Grease a 9x13-inch baking dish.
In a medium bowl, combine the cherry pie filling and crushed pineapple. Spread this mixture evenly in the bottom of the prepared baking dish.
In another bowl, whisk together the flour, granulated sugar, baking powder, and salt.
Add the melted butter, egg, and vanilla extract to the dry ingredients. Mix until just combined.
Spread the batter over the fruit mixture in the baking dish, smoothing it out gently.
In a separate bowl, mix the rolled oats, brown sugar, and cinnamon. Sprinkle this mixture evenly over the batter.
Bake in the preheated oven for 30-35 minutes, or until the top is golden brown and a toothpick inserted into the center comes out clean.
Allow the cake to cool for about 10 minutes before serving warm.