Preheat the oven to 350°F (175°C). Grease and flour a 9×13 inch baking pan.
In a large mixing bowl, whisk together the flour, sugar, baking powder, baking soda, and salt.
In a separate mixing bowl, whisk together the eggs, oil, lemon juice, lemon zest, and buttermilk. Gradually add the wet ingredients to the dry ingredients and mix until just combined.
Pour the batter into the prepared baking pan.
In a small mixing bowl, combine the flour, sugar, melted butter, shredded coconut, and chopped pecans for the crunch topping. Sprinkle the mixture evenly over the cake batter.
Bake the cake in the preheated oven for 40-45 minutes, or until a toothpick inserted into the center comes out clean.
Let the cake cool for 10 minutes before removing it from the pan and transferring it to a wire rack to cool completely.
In a small mixing bowl, whisk together the powdered sugar, lemon juice, and lemon zest for the glaze. Drizzle the glaze over the cooled cake.