Apple Coffee Cake: moist sour cream cake layered with juicy apples & cinnamon-spiced streusel crumb topping. Makes such a nice breakfast, brunch, or snack!
Place the butter in a small pot and melt over low heat.
Add the flour, brown sugar, cinnamon, and salt, and toss to combine.
Preheat the oven to 350 degrees F, and mist a 9-inch springform pan with non-stick spray.
Place the flour, sugar, baking powder, baking soda, and salt in a large mixing bowl, and stir to combine.
Add the butter, and mix on medium-low speed until the mixture resembles damp sand (about 2 minutes).
Add the eggs, one at a time, mixing on low speed until smooth.
Scrape the bottom and sides of the bowl with a silicone spatula, then add the sour cream, lemon juice, and vanilla.
Beat on medium speed for about 1 1/2 minutes, to aerate the cake batter and build its structure.
Transfer about 2/3 of the batter to the prepared pan.
Top with the diced apples, sprinkle with half of the crumb topping, then spread the remaining batter on top (layers of cake batter may seem thin, but they will puff up as they bake).
Sprinkle the remaining cinnamon crumb mixture on top, then bake the cake for 40 to 50 minutes, or until a toothpick inserted in the thickest part of the cake comes out clean or with a few moist crumbs.
Stir the powdered sugar and milk together in a small bowl until smooth, then drizzle over the cake.
Dust the cake with additional powdered sugar, for garnish.
*Plain Greek yogurt can be substituted.