Blueberry Crumb Coffee Cake

I found this recipe at A Year in the Kitchen, and the recipe is adapted from a recipe by Dorie Greenspan.  This blueberry crumb coffee cake is really delicious, and even has enough crumb topping for -s!

Ingredients:

• 5 TBSP unsalted butter at room temp
• 1/4 c. sugar
• 1/3 c. light brown sugar (packed)
• 1/3 c. all purpose flour
• 1/4 tsp. salt
• 1/2 c. rolled oats

• 1 pint blueberries
• 2 c. 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 ground nutmeg
• 2/3 c. sugar
• grated zest of 1/2 lemon
• 3/4 stick (6 TBSP) unsalted butter at room temp
• 2 large eggs, at room temp
• 1 tsp. vanilla extract
• 1/2 c. buttermilk

1. Preheat oven to 350.
2. Butter an 8-inch square pan and put it on a baking sheet.
3. To make the crumbs: Put all the ingredients in a food processor and pulse just until the mixture forms clumps and curds and holds together when pressed. Scrape the topping into a bowl, press a piece of plastic wrap against the surface. Refrigerate until needed.
4. To make the cake: Using your fingertips, toss the blueberries and 2 tsp. of the flour together in a small bowl just to coat the berries; set aside.
5. Whisk together the remaining 2 cups flour, baking powder, baking soda, salt, cinnamon and nutmeg.
6. Working in the bowl of a stand mixer or in another large bowl, rub the sugar and zest together with your fingertips until the sugar is moist and aromatic; then add the butter and, with the paddle or whisk attachment, or with a hand mixer, beat the sugar with the butter at medium speed until light, about 3 minutes; then add the eggs one by one, beating for about 1 minute after each addition, then beat in the vanilla extract.  Do not be concerned if the batter looks curdled, it will soon smooth out. 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 ingredients).  You will have a thick, creamy batter. With a rubber spatula, gently stir in the berries. Scrape the batter into the buttered pan and smooth the top gently with the spatula.
7. Pull the crumb mix from the fridge and, with your fingertips, break it into pieces.  There is no need to try to get even pieces — these are crumbs, they are supposed to be lumpy and bumpy and every shape and size. Scatter the crumbs over the batter, pressing them down ever so slightly.
8. Bake for 55 to 65 minutes, or until the crumbs are golden and a thin knife inserted into the center of the cake comes out clean.
9. Transfer the cake to a rack and cool just until it is warm or until it reaches room temperature.

Blueberry Crumb Coffee Cake: