I love blueberry crumb cake. My nana used to make a blueberry buckle cake which is soo similar to this. I found this recipe at A Cookie a Day's blog and she got it from Baking from my home to yours by: Dorie Greenspan
For the crumbs:
5 Tbsp unsalted butter at room temp
1/4 Cup sugar
1/3 Cup packed light brown sugar
1/3 Cup all purpose flour
1/4 tsp salt
1/2 Cup Chopped walnuts (I omitted)
For the cake:
2 Cups blueberries (preferable fresh)
2 Cups plus 2 tsp all purpose flour
2 tsp baking powder
1/2 tsp baking soda
1/4 tsp salt
1/4 tsp ground cinnamon
1/8 tsp freshly grated nutmeg (I didnt use fresh)
2/3 Cup sugar
Grated zest of 1/2 lemon or 1/4 orange
3/4 stick unsalted butter (at room temp)
2 large eggs
1 tsp vanilla extract
1/2 cup buttermilk
Center a rack in the oven and preheat the oven at 350 degrees. Butter an 8 in square pan and put it on a baking sheet.
To make the crumbs- put all the ingredients except the nuts(if you use nuts) in a food processor and pulse just until the mixture forms clumps and holds together when pressed. Scrape the topping into a bow, stir in the nuts and press a piece of plastic againt the surface. Refrigerate.
To make the cake- Toss teh blueberries and 2 tsp of the flour in a small bowl. Set aside. Whisk together the remaining 2 cups of flour, baking powder, baking sode, salt, cinnamon and nutmeg.
Working in a bowl of a stand mixer- rub the sugar and zest together with your fingers until the sugar is moist. Add the butter and mix at medium speed until light. Add the eggs one by one beating for about 1 minutes after each addition. Then add the vanilla extract. Reduce the mixer speed to low and add the flour mixture and the buttermilk alternately, the flour in 3 parts and the buttermilk in 2 (begin and end with the dry ingred) Gentrly stir in the berries with a spatula.
Scrape the batter into the buttered pan and smooth the top with a spatula. Break the crumb mixture with your fingers and scartter the crumbs over the batter- pressing them down slightly.
Bake for 55-65 minutes or until the crumbs are golden and a thin knife inserted comes out clean. Transfer the cake to a rack and cool.