Preheat the oven to 350 degrees Fahrenheit.
Line an 8x8 aluminum baking pan with parchment paper and set aside.
Whisk together the cinnamon and sugar for the filling and set aside.
Melt the butter for the streusel and use a fork to carefully mash in the remaining ingredients until it looks crumbly. If it looks too wet, add in more flour, if it looks too dry/crumbly, add in a splash of maple syrup or milk until it holds together a bit better.
In a large mixing bowl, beat together the wet ingredients for the cake with an electric mixer. Whisk in the dry ingredients until you get a smooth batter. Be sure to spoon and level the flour into your dry measuring cup to measure, don't scoop right from the bag.
Add half of the batter to the prepared pan, sprinkle on top the cinnamon sugar, then add in the remaining batter and spread evenly on top.
Use your fingers to crumble on the streusel.
Bake for 37-43 minutes or until a toothpick comes out clean. 40 is generally best in my oven, but all ovens are different so keep an eye on it.
Remove from the oven and let cool completely. I use the maple glaze from my healthy pumpkin bread to finish it off, but this is totally optional!