Preheat your oven to 350°F (175°C). Grease and flour a cake pan.
In a mixing bowl, whisk together the flour, sugar, baking powder, and salt.
In another bowl, combine the melted butter, eggs, vanilla extract, milk, lemon zest, and lemon juice.
Pour the wet ingredients into the dry ingredients and mix until just combined.
Pour the batter into the prepared cake pan and smooth the top.
Bake for 45 minutes or until a toothpick inserted into the center comes out clean.
Let the cake cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.