• Before you start, read through the entire recipe. Yes, this coffee cake uses a few bowls, but they’re necessary for the mixing method and getting the best texture from the cake.
• Preheat the oven to 350F degrees and adjust the oven rack to the middle position. Grease a 9x13-Inch baking dish. Or, if you plan to lift the whole cake from the dish, line it completely with parchment paper or foil, leaving an overhang on the sides to lift the cake. Lightly grease the paper/foil.

Streusel

• To toast the pecans (optional): Spread them on a small, parchment-lined baking sheet and put them in the oven while it's preheating. Toast for 5 to 7 minutes. You'll smell their toasty aroma, but watch them closely, as they can go from toasty to burned quickly. Once they are cool enough to handle, chop them into small pieces about the size of a pea.
• In a medium mixing bowl, whisk together the flour, both sugars, cinnamon, and salt. Add the butter cubes and cut into the mixture using two forks, your fingers, or a pastry cutter. Mix until you have coarse crumbs, then stir in the pecans.
  1 cup all-purpose flour, 3/4 cup granulated sugar, 1/2 cup dark brown sugar, packed, 2 tablespoons ground cinnamon, 1/2 cup unsalted butter, cold and cut into cubes, 1 cup pecans, finely chopped, 1/2 teaspoon salt
  

Coffee Cake

• In a small mixing bowl, add the applesauce, sour cream, and vanilla. Mix until combined and smooth. Set aside.
  1 cup unsweetened applesauce, room temperature, 1 ½ cups full-fat sour cream, room temperature, 2 tablespoons vanilla extract
• In a medium mixing bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.
  2 ¼ cups all-purpose flour, 1 tablespoon baking powder, 3/4 teaspoon baking soda, 3/4 teaspoon salt
• In the work bowl of a stand mixer fitted with the paddle attachment, add the butter and sugar. Mix on medium-high speed to cream the butter and sugar together until light and fluffy. Add the eggs, one at a time, and mix well after each addition. Scrape down the sides and bottom of the bowl as needed — the butter likes to stick to the bottom.
  1/2 cup unsalted butter, room temperature, 1 cup granulated sugar, 2 large eggs, room temperature
• Turn the speed to low and sprinkle half of the dry ingredients into the stand mixer bowl. Mix until just combined, then beat in the applesauce mixture. Add the remaining dry ingredients, turn the speed up to medium, and mix until no dry streaks remain and the batter is mostly smooth, scraping down the sides and bottom of the bowl as needed. The batter will resemble thick pancake batter, and it’s okay if there are a few lumps. Be careful not to overmix, or the cake can turn out tough.
  
• Pour half of the batter into the prepared baking dish and spread it to the edges with a spatula. Sprinkle about 1/3 of the streusel evenly over the top. Add the remaining batter and gently spread it over the streusel. Finish with the remaining streusel on top.
  
For the final streusel layer, squeeze the mixture together in your hand, then break it into clumps as you sprinkle it over the batter. The larger pieces will bake up extra crunchy.
• Bake the cake for 45 to 60 minutes, or until the edges of the cake are golden and a toothpick inserted in the middle comes out clean. Cool the cake completely in the baking dish, set on a wire cooling rack. This can take up to 2 hours. If you intend to lift the cake out of the dish to slice and serve, use the paper/foil overhang and lift carefully to prevent the cake from splitting.
To cut the cake into squares, I recommend using a serrated knife to break through the streusel top and not squash the cake.
• Cover the cake and store at room temperature for up to 3 days, or in the refrigerator for up to 5 days.