Preheat your oven to 325 degrees and grease an 8x8 pan with cooking spray and line it with parchment paper.
Prepare your topping by combining all topping ingredients in a small bowl. Set aside
In another small bowl, combine the oat flour, baking soda and salt. Mix and set aside.
In a large bowl, whisk the eggs, applesauce, coconut sugar, almond milk, vanilla, lemon juice, and lemon zest. Whisk until fully combined and smooth.
Pour the wet ingredients into the dry ingredients and fold just until combined.
Now, gently fold in to blueberries into the mixture. And pour your batter into prepared loaf pan.
Add your crumble topping and bake at 325 for 30-40 minutes (until the center fully cooked and center is done).
Let the coffee cake cool slightly before enjoying!