Apple Crumble Coffee Cake

I made this kinda last minute last night. I rushed through it and crossed my fingers that I didn't muck up with halving the recipe. 

I used sour cream instead of yogurt and baked in an 8 x 8 inch pan. I lucked out 'cause it came out good. I found the recipe here at the Allrecipes website.

Ingredients

• Dry Ingredients:
• 2 teaspoons unsalted butter
• 2 cups all-purpose flour
• 1/2 teaspoon fine sea salt
• 1 teaspoon baking powder
• 3/4 teaspoon baking soda
• 
  
• Crumble Mixture:
• 1 1/2 cups finely chopped toasted walnuts
• 1/3 cup packed light brown sugar
• 1/3 cup white sugar

 1/4 teaspoon salt

• 1 teaspoon ground cinnamon
• 3 tablespoons unsalted butter, melted
• 
  
• Wet Ingredients:
• 1/2 cup unsalted butter, at room
• temperature
• 1 cup white sugar
• 2 large eggs
• 1 1/2 teaspoons vanilla extract
• 1 cup plain yogurt
• 2 Honeycrisp apples

Directions

Preheat oven to 350 degrees F (175 degrees C). Butter a 9x12-inch baking dish generously.

Whisk flour, sea salt, baking powder, and baking soda together in a bowl. Set aside.

Combine walnuts, brown sugar, white sugar, salt, cinnamon, and melted butter in a bowl. Mix until walnuts and sugar are thoroughly coated with butter.

Cream butter and sugar together in another bowl with a spatula until well blended. Add 1 egg and whisk until mixture is smooth, 2 to 3 minutes. Whisk in second egg until thoroughly incorporated. Add vanilla extract and yogurt; whisk together. Add flour mixture to wet ingredients; whisk just until flour disappears. Do not overmix.

Remove cores from apples. Cut across into 1/8- to 1/4-inch slices. Stack up a few slices, make 1 cut down the center, and dice across into cubes. Add to cake batter, folding in with a spatula until just combined.

Spread 1/2 of the batter evenly into the bottom of the prepared baking dish. Scatter 1/2 of the crumble mixture evenly over the top. Top with the rest of the batter in dollops. Spread carefully to evenly distribute, trying not to disturb the crumbs. Top with the rest of the crumb mixture. Press crumbs into the batter very gently.

Bake in the center of the preheated oven until a toothpick or bamboo skewer inserted into the center comes out clean, about 40 minutes. Let cool to room temperature, about 30 minutes, before slicing and serving.