For the cake:
Set a rack in the center of the oven and preheat to 350 F. Butter and flour a large baking tray or sheet pan, 11 x 15-inch or 11 x 17-inch.
In a medium size bowl, sift together the flours, baking soda, baking powder, spices and salt. In a separate bowl, whisk together the eggs, maple syrup, applesauce and melted butter. Make a well in the center of the dry ingredients and scrape in the egg mixture, whisk gently or stir with a wooden spoon. Add the apple cubes. Do not over mix. Transfer to the prepared pan and smooth the top.
For the streusel:
Combine the oats, almonds, and brown sugar. Work in the butter using your fingertips until crumbly. Sprinkle evenly over the top of the batter.
Bake for about 24 - 30 minutes, until the cake springs back when pressed gently with a finger. Baking time will vary based on the size of the pan used.