Preheat the oven to 350 degrees, and grease an 8x8 inch cake pan generously. Line with a piece of parchment paper, with the edges overhanging for easy removal. 

In a small bowl, whisk together the flour, cocoa powder, baking soda, and salt. Set aside. In a large bowl, beat together the butter, oil, and sugar until fluffy. Add in the egg and vanilla and beat until combined. 

In a small bowl, whisk together the vinegar, buttermilk, and red food coloring. Add the flour mixture and the buttermilk mixture to the butter mixture in alternating additions, starting and ending with the flour mixture. Beat until just combined and no dry spots remain. 

Pour the batter and spread evenly into your prepared cake pan. Set aside. 

In a medium bowl, use a fork to mix all the ingredients together until a crumbly mixture forms. Add a tablespoon more butter if the mixture is too dry, or a tablespoon more flour if it is too wet. You want to be able to press the mixture together and get large crumbs. 

Sprinkle the crumbs evenly over the top of the cake batter. It will seem like a lot, because it is, but use it all! Bake for 38-40 minutes, or until a cake tester comes out clean. Cool completely, remove from the pan, and slice and serve!