Grate the lemon zest and set aside. Blend the remaining lemon, removing as much white pith as possible. In a blender, combine the lemon, eggs, and vegetable oil. Blend until smooth. Add sugar, flour, and baking powder to the blender. Blend again until fully incorporated. Using a rubber spatula, gently mix in the lemon zest.
Grease a 23x10 cm (9x4 inch) loaf pan and pour in the batter. Preheat oven to 350°F (180°C) and bake for 45 minutes.
Let the cake cool in the pan for 10 minutes before transferring to a wire rack. Slice and enjoy!
