Preheat oven to 350*F Grease an 8-inch square baking pan and line it with parchment.
In a medium bowl, combine flour, baking powder, baking soda, and salt. Whisk and set aside.
1 ¾ Cups All-Purpose Flour, 1 ½ tsp Baking Powder, ¼ tsp Kosher Salt, ¼ tsp Baking Soda
In a large bowl, combine sugar, applesauce, melted non-dairy butter, non-dairy milk, and vanilla. Stir to combine.
⅔ Cup Granulated Sugar, ⅔ Cup Unsweetened Applesauce, ¼ Cup Non-Dairy Milk, 1 tsp Vanilla Extract, 7 Tbsp Non-Dairy Butter, melted and cooled
Add the dry ingredients to the wet ingredients and stir just until the batter is formed. Then, add the cinnamon apple mixture and fold them into the batter with a spatula just until the apple is distributed and there are streaks of cinnamon throughout the batter.
Scrape the batter into a prepared 8-inch square baking pan and use a spatula to spread it evenly into the corners. Then, squeeze handfuls of the crumb topping in your hands to make it stick together and lightly break it up evenly over the batter. This will help create big crumb chunks. Then, gently press the crumb into the batter with your hands.
Bake in a 350* F oven for 40-43 minutes or until a toothpick inserted into the center of the cake comes out clean.
Allow the crumb cake to cool in the pan for 30 minutes, then gently move it to a cutting board to continue cooling.
Dust with powdered sugar, if desired, slice and serve.
1 Tbsp Powdered Sugar