Preheat the oven to 350 degrees F. Lightly coat a 9-by-13-inch baking dish with cooking spray.
Place a large skillet over medium heat. Add the apples, butter, agave and salt; mix and let simmer down for 10 minutes. Remove from the heat and allow to cool down.
In a large bowl, combine the cooked apples, peaches, cornstarch, almond extract and cinnamon and mix well. Zest half of the orange into the mixture and mix again.
Place one of the rolled-out pie crusts in the bottom of the prepared baking dish. Bake until very light brown, about 5 minutes. Remove from the oven and add about half of the fruit filling to the baking dish, filling it about halfway. Cover the fruit with the second pie crust. Bake until golden brown, another 10 minutes.
Add the remaining fruit mixture, filling the baking dish to the top. Cover the cobbler with the third rolled-out pie crust and pinch it to the rim of the baking dish to seal. Cut 3 slits across the top of the crust, brush on the egg yolk and sprinkle with the brown sugar. Zest the remainder of the orange over the top.
Bake until the fruit juices are bubbling and the crust is a dark golden brown, about 40 minutes.