Pre-heat oven to 3500F
Grease or line an 8” x 8” baking pan
Make topping by mixing flour, brown sugar, cinnamon and ground flax together in a bowl. Cut in butter using a pastry cutter to achieve a coarse meal texture. Set aside.
Combine the almond milk with the apple cider vinegar in a medium bowl.
In a separate large bowl, sift together the flour, sugar, baking soda, baking powder and salt.
Once the almond milk starts to curdle, mix in the unsweetened apple sauce, the flax oil, and the vanilla.
Add the liquid ingredients to the dry ingredients and mix until just combined.
Spread 1⁄2 of the batter in the prepared baking pan, and sprinkle with 1⁄2 of the topping mixture
Spread the remaining batter on top, and sprinkle with the remaining topping mixture.
Bake at 3500F for 40 minutes.