Preheat the oven to 350ºF or 180ºC. Grease two 9-inch (23 cm) cake pans. I also line the bottoms with a circle of parchment paper. Set aside.

Mix the plant milk and vinegar in a jar or bowl until well combined. Let the mixture rest at room temperature for at least 5 minutes. After this time, the milk will thicken and curdle.

In the meantime, add the dry ingredients to a large mixing bowl (flour, sugar, baking powder, baking soda, and salt) and mix until combined.

Add the oil, vanilla extract, lemon zest, lemon juice, and the plant milk and vinegar mixture. Stir until well combined.

Divide the batter evenly between the two cake pans. 

Bake for about 30 to 40 minutes or until a toothpick inserted in the center comes out clean. Baking time may vary depending on the oven.

Let it cool for 15 minutes before transferring it to a cooling rack and then let it cool completely before frosting. If you don’t have a cooling rack, just use a dish or what you have on hand.

Add the vegan butter to an electric mixer bowl and beat until light and fluffy. You could also use a regular large bowl and a hand mixer. 

Then add the lemon juice, lemon zest, and vanilla extract, and beat once more.

Gradually add the powdered sugar, ½ cup (120 g) at a time, and continue mixing until thick and creamy.

If your frosting is too thick or crumbly, add a little bit of unsweetened plant milk (soy milk is my favorite one). If your frosting is too thin, just add more powdered sugar until it thickens.

Frost the cake using an icing spatula or a butter knife, adding a thick layer between the top and bottom layers. 

Slice your vegan lemon cake and serve. Ideally, refrigerate the cake for 30 minutes before serving, but this is optional.

Store the leftovers in an airtight container in the fridge for 3 to 5 days. You can also freeze it for up to 1 month, but in that case, freeze the cake without the frosting and frost it right before serving.