Preheat the oven to 375 degrees F.
Sift together the flour, granulated sugar, baking powder and salt. Set aside for a moment.
In a large bowl, whisk together the egg, milk and canola oil.
To the egg mixture, add about half of the dry ingredients and stir until smooth.
Add the remaining dry ingredients and stir until smooth (the dry ingredients are added to the egg mixture in a couple batches so that it's easier to mix it into the wet ingredients).
Grease the baking dish or pan (9 x 9 x 2) with butter.
Add the batter to the pan. Use a spatula to spread the batter evenly in the pan.
Add the blueberries evenly on top of the batter.
Sprinkle the streusel evenly on top.
Bake in a preheated oven for 25 minutes or until a toothpick inserted in the middle of the cake comes out clean.
After removing the cake from the oven (keep the cake in the pan), make the lemon glaze (it needs to be drizzled on top of the cake while the cake is warm).