Preheat your oven to 350°F and lightly spray an 8×8-inch square baking dish with cooking spray.
In a small bowl, whisk together the non-dairy milk, lemon zest, and lemon juice. Set aside for 5 minutes to allow the mixture to slightly curdle.
In a large bowl, whisk together the date sugar and olive oil until smooth. Add the milk mixture and whisk again to combine.
In a medium bowl, mix the gluten-free flour, baking soda, and sea salt. Fold the dry ingredients into the wet ingredients, stirring just until combined.
Pour the batter into the prepared pan and smooth the top. Bake for 35 minutes, or until a toothpick inserted in the center comes out clean.
Remove from the oven and let cool for at least 10 minutes in the pan. Transfer to a cooling rack and allow the cake to cool completely before topping with your favorite vegan frosting!