Preheat the oven to 350 degrees.

Combine the soy milk and apple cider vinegar and set aside.

Whisk the flour, baking soda, baking powder, and salt together in a large mixing bowl. In a separate bowl, combine the curdled soy milk, oil, sugar, vanilla extract, and Garam Masala. Mix the wet ingredients with the dry ingredients.

In a separate bowl, mix the brown sugar, margarine, and flour with your fingertips to form course crumbs for the topping.

Pour the batter into a baking dish and sprinkle on the topping in an even layer.

Bake for 30 to 40 minutes, or until the top looks crispy and golden and a toothpick inserted at the center of the cake comes out clean. Allow to cool before cutting and serving.