Preheat your oven to 350°F (175°C). Grease a 9x13-inch baking dish or line it with parchment paper.
In a large mixing bowl, combine the flour, granulated sugar, baking powder, and salt. Mix well.
Add the softened butter, eggs, vanilla extract, and milk to the dry ingredients. Beat with an electric mixer on medium speed until the batter is smooth and well combined, about 2-3 minutes.
Gently fold in the blueberries with a spatula, being careful not to crush them.
Pour the batter into the prepared baking dish, spreading it evenly.
In a small bowl, mix the cinnamon, brown sugar, and chopped nuts (if using) for the topping. Sprinkle this mixture evenly over the batter.
Bake in the preheated oven for 35-40 minutes, or until a toothpick inserted into the center comes out clean.
Allow the coffee cake to cool in the pan for about 10 minutes before slicing and serving.