Combine the filling ingredients (blueberries, sugar, flour, juice and zest of half a lemon, cinnamon) in a bowl and toss to coat.

Place the blueberry mixture into a lined 4-qt Dutch oven.

To make the topping: combine flour, sugar, baking powder, and salt in the bowl and stir to mix. Add the butter and mix and mash with a fork or your hands until the flour and butter come together into pea sized pieces. Add the milk and stir to combine.

Drop the topping batter across the blueberries.

Cover the Dutch oven and place on a bed of 7 coals, adding 14 to the lid of the oven.

Cook for 40-45 minutes, giving the oven and lid a ¼ turn every 15 minutes and adding new coals if they die out, until the topping is golden brown.

Remove from the heat and set aside, uncovered, to cool a touch before serving with whipped cream.