Preheat the oven to 375°F (190°C) and grease a 9x13-inch baking dish.

In a large bowl, whisk together the flour, baking powder, and salt.

In a separate bowl, cream together the softened butter and granulated sugar until light and fluffy.

Beat in the eggs one at a time, then stir in the milk, canola oil, and vanilla extract until combined.

Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Do not overmix.

Gently fold in the blueberries.

Pour the batter into the prepared baking dish and spread evenly.

Bake for 30-35 minutes, or until a toothpick inserted into the center comes out clean and the top is golden brown. If the cake is browning too quickly, loosely tent it with aluminum foil during the last 10 minutes of baking.

While the cake is baking, prepare the glaze. In a small bowl, whisk together the confectioners' sugar and milk until smooth and pourable. Add more milk a teaspoon at a time if needed to reach desired consistency.

Once the cake is out of the oven, let it cool slightly in the pan. Drizzle the glaze over the warm cake.

Serve warm or at room temperature.