Place the ½ cup of unsalted butter into a 13×9 inch baking pan. Put the pan into the preheating oven to melt the butter. This should take about 5-7 minutes. Carefully remove the pan once the butter is melted, set aside.
Meanwhile, prepare the blueberry mixture. In a medium saucepan, combine 4 cups of fresh blueberries, 1 cup of sugar, 1 tablespoon of freshly squeezed lemon juice, and ¼ cup of water. Stir this mixture together to ensure the blueberries are well coated with sugar.
Place the saucepan on the stove over medium-high heat. Allow the mixture to come to a gentle boil, stirring occasionally to prevent the sugar from burning.
In a large mixing bowl, combine 2 cups of all-purpose flour, 4 teaspoons of baking powder, 1 teaspoon of salt, and 1 ½ cups of sugar. Mix these dry ingredients together until they’re evenly distributed.
Pour 2 cups of milk into the bowl with your dry ingredients. Stir this mixture together until it forms a smooth batter. Pour the batter directly into the pan containing the melted butter. Do not stir the batter and butter together.
Use a slotted spoon to scoop out the blueberries from your saucepan. Distribute the blueberries evenly over the top of the batter.. Bake in the preheated oven for 30-35 minutes, or until the top is golden brown and a toothpick inserted into the center of the cake comes out clean.
Use a slotted spoon to scoop out the blueberries from your saucepan. Distribute the blueberries evenly over the top of the batter.. Bake in the preheated oven for 30-35 minutes, or until the top is golden brown and a toothpick inserted into the center of the cake comes out clean.