Preheat oven to 350F and line your baking pan with parchment and spray with oil.
Combine crumb topping ingredients, chill while making the cake batter.
Add vinegar to milk, set aside as buttermilk substitute.
In a bowl, whisk together flour, sugar, baking powder, baking soda, salt.
Add oil, vanilla and buttermilk substitute gradually and whisk until combined into a pourable cake batter. You may not need the entire buttermilk mixture. Don't overmix, stopping as soon as no dry pockets of flour remain.
Pour 1/2 cake batter into your pan and sprinkle 1/2 the crumb topping. Repeat again.
Bake 30-40 minutes until the cake is fully baked.
Cool, slice and enjoy!