• Preheat oven to 350. Grease a 9x13 brownie/ baking pan.

Cake

• Mix together the sugar, flour, baking powder and salt, and make a well in the center.
  
• Add the egg, milk, oil, and vanilla. Break up the eggs, and mix until completely combined.
  

Topping

• Mix the brown sugar, flour and cinnamon together in a large bowl, whisking to combine everything evenly.
  
• Using a cheese grater, grate the cold butter into the dry ingredients, tossing occasionally as you go to keep the butter from clumping.
  
• Once all of the butter is grated, use your hands to rub it into the dry ingredients until you have a crumb topping with pieces the size of peas.
  
• Pour the batter into the prepared pan, and spread evenly. Top with all of the crumb topping. Start at the edges, and work your way towards the center. This will help prevent the crumbs from sinking into the cake. It will seem like there is not enough batter and that there is too much topping -- don't worry once it's baked, it will be even.
  
• Bake 35-40 minutes until crumbs are golden and wooden skewer inserted into center of cake comes out clean. Cool on wire rack at least 30 minutes. Dust with confectioners’ sugar just before serving.