In a large bowl, stir together blueberries, sugar, and lemon zest until combined. Set aside.
For the Batter:
Place the butter in a 8x8-inch baking dish. Place the dish in the preheated oven until the butter is melted, about 10 minutes.
Meanwhile, in a medium mixing bowl, whisk together the flour, sugar, baking powder, and salt. Whisk in the milk until just combined.
Carefully remove the baking dish from the oven, and pour the batter into the pan (do not stir). Top evenly with the blueberry mixture. Sprinkle with coarse sugar.
Bake for 40 to 45 minutes or until the batter is golden brown and a wooden pick inserted in the center comes out mostly clean. Let the cobbler cool slightly before serving. Serve with a scoop of vanilla ice cream, if desired.
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Notes
A note on butter: Some butter may float to the top and not reabsorb until the cobbler is almost done, so don't panic if it still looks wet until the last few minutes of baking.
Don't add more berries. This will increase the baking time and cause the cobbler to burn at the edges or be underbaked in the center.
Control the sweetness. If the blueberries are not as sweet as you'd like, feel free to add more sugar to them.
Add lemon juice. If you love lemon flavor, add about half a tablespoon of lemon juice to the blueberries in addition to the zest.
Use a 9x13-inch pan. You can bake this same recipe in a larger pan. Reduce the baking time to 30 to 35 minutes, as the cobbler will be a bit thinner and bake faster.