Preheat your oven to 350°F (175°C). This ensures that the cobbler bakes evenly.

In a large mixing bowl, combine the sliced peaches and raspberries.

Add the granulated sugar, flour, vanilla extract, and lemon juice to the fruit. Gently toss to coat the fruit evenly. This will help to create a syrupy filling as it bakes.

Transfer the fruit mixture to a greased 9x13-inch baking dish, spreading it out evenly.

In a separate mixing bowl, whisk together the flour, baking powder, salt, and sugar.

Add the cold butter pieces to the flour mixture. Using a pastry cutter or your fingers, work the butter into the flour until the mixture resembles coarse crumbs. This creates a flaky texture in the biscuits.

Pour in the cold buttermilk and stir gently with a spatula until just combined. Do not overmix, as this can lead to tough biscuits.

Using a spoon or ice cream scoop, drop spoonfuls of the biscuit dough over the fruit filling. Leave some gaps for the fruit to bubble up.

Sprinkle the tablespoon of sugar over the biscuit topping for added sweetness and a nice crust.

Place the baking dish in the preheated oven and bake for 35-40 minutes, or until the topping is golden brown and the fruit is bubbling. The baking time may vary based on your oven.

Once baked, remove the cobbler from the oven and let it cool for about 10-15 minutes before serving. This allows the juices to thicken slightly.

Serve warm, optionally with a scoop of vanilla ice cream or whipped cream on top for a delightful contrast.