Preheat your oven to 350°F (175°C).
Grease and line an 8-inch square baking dish with parchment paper.
In a large bowl, whisk together the flour, granulated sugar, baking powder, baking soda, ground cinnamon, and salt.
In another bowl, mix the dairy-free milk, vegetable oil, vanilla extract, and apple cider vinegar until well combined.
Add the wet ingredients to the dry ingredients, mixing until just combined.
Pour half of the batter into the prepared baking dish and spread it evenly.