Preheat oven to 350 degrees F. Slice butter into pieces and add to a 13x9-inch baking dish. Place the pan in the oven while it preheats, allowing the butter to melt. Once melted, remove the pan from the oven and set aside.
In a bowl, add blueberries, ½ cup of sugar and zest. Stir to combine.
In a separate bowl, mix together flour, 1 cup of sugar, baking powder and salt. Stir in the milk, just until combined.
Pour the sugared/zested blueberries over melted butter in pan. Drizzle batter over the top. Sprinkle with a little bit of cinnamon.
Bake for about 35 minutes, or until lightly golden on top. Serve warm with a scoop of vanilla ice cream, if desired.
