Preheat the oven to 350 °F (180 °C). Line a 6-inch round cake pan with parchment paper. Oil the side and bottom nicely to prevent the cake from sticking to the pan. Set aside.
In a mixing bowl, whisk the self-rising flour, sugar, and salt if used.
Pour the fresh lemonade, oil, and lemon extract if used. Use a rubber spatula to stir and form a smooth cake batter.
Pour the batter into the prepared pan.
Bake the cake for 50-60 minutes on the center rack of the oven at 350 °F (180 °C), foiling the top of the pan after 40 minutes to prevent the cake from darkening too fast.
Bake until golden brown on top and a pick inserted in the center of the cake comes entirely clean.
Let the cake cool down in the pan at room temperature for 10 minutes, then gently unmold on a cooling rack and cool for 2 hours before slicing.
