Light a campfire and let it burn down to a bed of glowing coals. You'll want about 20-25 coals for a 10-inch dutch oven.
In a large bowl, combine the berries, 1/2 cup sugar, cornstarch, lemon zest, and lemon juice. Stir gently and set aside.
In a separate bowl, whisk together flour, remaining 1 tablespoon sugar, baking powder, and salt. Cut in the cold butter using your fingers or a fork until the mixture resembles coarse meal. Pour in the milk and stir just until a shaggy dough forms. Do not overmix.
Place your dutch oven over a small pile of coals to preheat for 2-3 minutes. Pour the berry mixture into the hot pot. Drop spoonfuls of biscuit dough over the berries, spacing them evenly.
Cover the dutch oven with its lid. Using tongs, arrange about 10-12 hot coals on top of the lid. Place the pot on a heat-safe surface (like a flat rock or the fire ring's edge) with a few coals underneath—about 8 coals should do.
Cook for 20-25 minutes, rotating the pot and lid a quarter turn every 10 minutes for even heat. The cobbler is done when the biscuits are golden brown and the berries are bubbling thickly around the edges.
Carefully remove the lid using a lid lifter or heavy glove, watching for steam. Let cool for 5-10 minutes before serving. Spoon into bowls and enjoy as is, or with a dollop of yogurt or cream if you brought it.