Preheat oven to 375 F/190 C. Grease and flour a 13 x 9" pan.
Combine the milk and lemon juice together, and set aside to curdle.
Mix all topping ingredients together in a medium bowl until crumbly.
In a large mixing bowl, combine curdled milk, sugar, oil, and vanilla. Then add all the dry ingredients and mix until smooth. Pour cake batter into prepared pan and let it rest for 15 minutes before adding topping.
Sprinkle topping evenly over batter, then bake for 35-45 minutes, until a toothpick stuck into the center of the cake comes out clean.
Allow the cake to cool for about 15 minutes before serving. Keep in an airtight container or covered in the pan for up to 5 days.
Notes
Heavily adapted from Isa Chandra Moskowitz's East Coast Coffee Cake recipe from her book Vegan Brunch.