Preheat the oven to 350 degrees Fahrenheit. Then, grease the 9×13 inch cake pan.
Afterward, whisk in a mixing bowl the flour, sugar, baking powder, baking soda, and salt.
In a mixing bowl of a hand or stand mixer fitted with a whisk attachment, add the vegetable oil and eggs, then gradually add the sugar; beat on medium-high speed.
Afterward, add the flour and sour cream to the egg mixture on low-medium speed for a minute or well incorporated.
Then, turn the mixer off; using a rubber spatula, fold in the vanilla and blueberries until it is thoroughly mixed. After that, pour the batter mixture into the prepared greased 9×13 inch cake pan.
Then, take the crumb mixture out from the freezer. After that, evenly sprinkle it over the cake batter.
Afterward, bake in the oven for 50 to 55 minutes or until a skewer inserted in the center comes out clean. Next, place in a wire to cool for 20 minutes, then serve warm and enjoy!