Preheat your oven to 350 degrees. Generously grease a loaf pan, and line it with parchment paper that overhangs in the edges.
In a medium bowl, add all of the cake ingredients. That seems weird, but I promise it works well here. Beat everything together until you have a thick batter that is well-combined, about 2 minutes.
Spread the batter evenly into your prepared cake pan. Set aside while you make the crumb.
In a medium bowl, mix together all of the crumb ingredients with a fork until crumbs form. It will take a few minutes to completely combine, but it should have a texture where crumbs form easily. If it's too wet, add a touch more flour, and if it's too dry and crumbs won't form, add a touch more melted butter.
Sprinkle the crumb topping evenly over the cake batter in your pan. It's going to seem like a lot of crumb- that's because it is! Use it all! You shouldn't see any cake batter coming through.
Bake the cake for 20-22 minutes, or until a toothpick comes out clean and the top is lightly golden brown. Cool completely until removing from the pan and slicing. Enjoy!