Preheat the oven to 350°F (175°C). Grease and flour a 9-inch round or square cake pan.
In a bowl, whisk together flour, baking powder, baking soda, and salt.
Beat butter and sugar until creamy. Add eggs, lemon zest, lemon juice, and vanilla.
Mix in the dry ingredients, alternating with sour cream.
Pour the batter into the prepared cake pan.
In a small bowl, combine shredded coconut, sugar, and lemon zest. Sprinkle evenly over the batter.
Bake for 30 minutes or until a toothpick comes out clean.
Cool for 10 minutes before serving.