Preheat and Prepare Pan: Position a rack in the center of your oven and preheat to 375°F (190°C). Lightly grease your skillet or baking dish with cooking spray or a neutral oil.

Craft the Cobbler Topping: In a medium bowl, whisk together the whole wheat pastry flour and sea salt. In a separate smaller bowl, whisk the egg white until it's frothy. Stir in the low-fat milk, maple syrup, and vanilla extract. Pour the wet mixture into the dry ingredients and stir with a spatula just until a soft, uniform batter forms. Avoid overmixing. Set the batter aside to rest for a few minutes.

Mix the Fruit Base: In the second medium bowl, combine the cornstarch, coconut sugar, cardamom, and nutmeg. Add the chopped apples, raspberries, blueberries, orange zest, and orange juice. Gently fold everything together until the fruit is evenly coated in the spiced sugar mixture.

Assemble the Bake: Scrape the fruit mixture into your prepared skillet or baking dish and spread it into an even layer. Spoon dollops of the topping batter over the fruit, leaving some small gaps for the filling to bubble through. It doesn't need to be perfectly smooth.

Bake to Golden Perfection: Sprinkle the demerara sugar evenly over the topping. Place the dish in the preheated oven. Bake for 35 to 40 minutes. The cobbler is ready when the fruit filling is bubbling vigorously around the edges and the topping is a deep golden brown.

Cool and Serve: Carefully remove the dish from the oven and let it cool on a wire rack for at least 15 minutes before serving. This allows the filling to set slightly. Serve warm.