Line an 8x8 pan with parchment paper and preheat oven to 350 degrees
Combine the flour and baking powder together. In a separate bowl, whisk egg yolks (set egg whites aside for later - very important!) and butter together. Then add honey, lemon juice, lemon zest, vanilla extract and mix thoroughly
Add wet mixture into dry and combine until smooth. Fold in egg whites until well combined, but do not to over-mix
Bake for 20-25 minutes
Whisk together icing. Let cake cool, top with icing and refrigerate until icing hardens.