Begin by preheating your oven to 350°F/180°C. To prepare the pan, line an 8"x8"  baking dish with parchment paper.

In a medium mixing bowl, combine the almond milk with vinegar, brown sugar, apple puree, vanilla extract, and vegetable oil. Whisk these ingredients until they are combined.

In another bowl, mix together the flour, baking powder, salt, and baking soda.

Pour the wet ingredients into the dry ingredients and mix until a smooth batter is formed.

Pour the batter into the lined baking pan.

For the crumbly topping, mix flour, sugar, salt, and cinnamon in a separate bowl. Using your fingers, work in butter until the mixture resembles crumbs.

Evenly sprinkle the crumbled topping over the batter in the pan, then place the dish in the oven. Bake for 35-45 minutes, or until a toothpick inserted into the center of the cake comes out clean.