Preheat the oven to 350°F (180°C) and spray two 8-inch (*see notes) cake pans with non-stick spray and line the bottoms with circles of parchment paper.
Sift all purpose flour into your mixing bowl and add white granulated sugar, baking soda and salt. Mix together.
Add milk, oil, lemon juice, vanilla extract, lemon extract and lemon zest and mix into a batter. Don't over-mix.
Divide the batter evenly between the two prepared 8-inch cake pans.
Bake for 30 minutes or until a toothpick inserted into the center of one of the cakes comes out clean.
Let the cakes cool in the cake pans for a few minutes and then remove them from the pans and place them onto a wire cooling rack to cool completely before frosting.
Prepare your frosting. Add softened butter to the bowl of your stand mixer and starting at slow speed, gradually increase speed and let it whip for around 3 minutes until your butter is smooth and pale in color.
Add powdered sugar, lemon extract and lemon juice and beat for around 5-6 minutes until very fluffy and smooth.
When the cakes are completely cooled, frost with the lemon buttercream frosting.