For curd: Prepare curd by whisking sugar, lemon zest, lemon juice and butter cubes in a small saucepan over medium-low heat.
Once butter is melted, whisk in eggs, one at a time, incorporating thoroughly. Whisk constantly until mixture thickens and bubbles start to come to the surface, about 15 minutes. (Note: You must whisk the entire time or the eggs might curdle and cook separately from the curd.)
Once curd is thick and starting to boil, remove the pan from the heat and let curd cool slightly in the refrigerator until ready to use. (It thickens more as it cools.)
For crust and topping: Preheat oven to 350 degrees. In the bowl of a stand mixer, cream butter and sugar until light and fluffy. Combine flour and baking soda. Gradually add to creamed mixture and mix well.
Set aside 1 cup mixture for the topping. Press remaining mixture onto the bottom of a lightly greased 13-by-9-inch baking dish. Bake for 12 to 15 minutes or until edges are lightly browned. Cool for 10 minutes.
For bars: Spread lemon curd over crust. In a small bowl, combine coconut, toasted almonds and reserved topping mixture. Sprinkle over lemon curd.
Bake for an additional 18 to 22 minutes or until golden brown. Cool completely on a wire rack. Cut into bars. Store in an airtight container in the refrigerator.