Blackberry Pineapple Upside Down Cake

Directions

1. Heat the oven to 350°, F. Oil, butter, or spray a 9-inch cake pan that is at least 2 inches deep with cooking spray and line the bottom with parchment paper. (If your cake pan is less than 2 inches deep, divide between 2 pans and start checking for doneness at 30 minutes.)
2. Combine pineapple, balsamic, and brown sugar in a 10-inch skillet, cook over medium heat, stirring occasionally during the first 5 minutes, until pineapple is translucent and has a light brown hue, 15 to 18 minutes. Empty fruit and juices into a mesh strainer or colander set over a medium bowl. Return juices to skillet, leaving pineapple in the strainer (you should have about 2 cups of cooked fruit). Simmer juices over medium heat until thickened, beginning to darken, and mixture forms large bubbles, 6 to 8 minutes, adding any more juices released by fruit to skillet after about 4 minutes. Off heat, whisk in butter. Pour caramel mixture into the prepared cake pan. Set aside while preparing the cake. (Pineapple will continue to release liquid as it sits, do not add this liquid to the already-reduced juice mixture.)
3. In a bowl, whisk the flour, sugar, salt, baking soda and powder. In another bowl, whisk the olive oil, milk, eggs, orange zest and juice. Add the dry ingredients, whisk until just combined. Pour drained pineapple onto caramel in the pan, gently spreading in an even layer. Pour the batter into the prepared pan and bake for 1 hour, until the top is golden and a cake tester comes out clean. Transfer the cake to a rack and let cool for 30 minutes.
4. Run a knife around the edge of the pan, invert the cake onto the rack and let cool completely for 2 hours.