Vanilla Blueberry Crumb Cake

I made this cake yesterday and the result is quite nice, the only downside is that mine was a bit bloated for what they call it crumble. But, nevertheless, it tastes good with soft texture (I like this kind of outcome) and it's not so sweet. The recipe itself is from 'Chocolate & Vanilla' by Gale Gand. So here's the recipe copied over from the book:
2 cups all purpose flour
1 cup granulated sugar
½ cup packed light brown sugar
1 cup unsalted butter
1 cup sour cream
1 large egg
1 tsp pur vanilla extract
1 tsp baking powder
1 tsp baking soda
½ tsp salt
1 pint blueberries

Preheat the oven to 350F. Butter and flour a 9’ square cake pan or line it with parchment paper and set it aside.

In a mixer fitted with the paddle attachment, combine 1 ½ cups of the flour, the granulated sugar, brown sugar, and butter on low speed until the mixture is blended and starts to forms clumps. Set aside 1 cup of the mixture to use for the crumb topping.
In a small bowl, whisk together the sour cream egg, vanilla, baking powder, baking soda, and salt until combined. Stir in the remaining ½ cup flour, then scrape this mixture into the mixer and beat on medium speed until it forms a smooth batter. Spread it into the prepared cake pan. Sprinkle the blueberries over the batter, press them down a little and then sprinkle with the reserved crumb topping.

Bake for 40 minutes or until the cake is form to the touch and a skewer or toothpick inserted into the center comes out clean. Let the cake cool in the pan set on the cooling rack.