Preheat the oven to 350° and lightly spray with non-stick cooking spray.
Peel, core, and dice apple into small pieces.
In a large microwave safe bowl, heat the butter in the microwave until melted.
Add the brown sugar and sugar to the bowl and whisk until the large clumps have dissipated.
Add eggs and vanilla, and whisk until the mixture becomes smooth.
Stir in flour, cinnamon, and a pinch of salt. The batter will be slightly lumpy. Do not overmix.
Add the diced apple and mix until just combined.
Spoon batter into the prepared brownie tin, or an 8x8 glass pan.
Cook for 25 minutes or until golden on the edges and the center is set or a toothpick inserted in the center comes out clean.
Remove from the oven and let cool.
Top with a scoop of vanilla ice cream and drizzle with caramel sauce.