Preheat your oven to 375°F (190°C).
In a medium bowl, combine the blueberries, sugar, and lemon juice. Mix well and set aside.
In another bowl, mix the Bisquick mix, milk, melted butter, and cinnamon (if using) until just combined.
Pour the blueberry mixture into a greased 8×8-inch baking dish. Drop the batter by spoonfuls over the blueberries.
Bake in the preheated oven for about 25-30 minutes, or until the top is golden brown and a toothpick inserted into the batter comes out clean.
Let it cool for a few minutes before serving. It’s best enjoyed warm with a scoop of vanilla ice cream or a dollop of whipped cream.