1. Separate egg yolks and whites. They are easier to separate when cold. Place into two separate, VERY clean bowls. Let them come to room temperature.
2. Prep your pan. Line the bottom of a 8-inch* spring form pan or cake pan with parchment paper and grease the sides. Preheat oven to 325° F.
3. Mix the yolks. In a bowl mix the yolks with honey, lemon zest, and vanilla until you get a smooth batter. Set aside.
4. Mix dry ingredients. In a separate bowl, whisk together almond flour, tapioca flour and baking powder.
5. Combine batter and dry ingredients. The batter will be quite thick. Set aside.
6. Whip egg whites. Using a hand mixer (or a whisk), whip egg whites on medium speed until just frothy. Pause and add a pinch of salt and 1 teaspoon lemon juice. Continue to whip, on high speed, until they reach the soft peaks stage. There should be no more liquid egg whites on the bottom of the bowl, and when the beaters are lifted out of the egg whites, the peaks should flop over slightly, (not so stiff that they stand straight up).
7. Gradually fold in the egg whites. Adding a little bit at a time, use a spatula to gently fold the whipped egg whites into the cake batter. At first it may seem like the whites won’t combine, but just keep going, gently folding the mixture together (don’t stir, just fold or you’ll deflate the batter). Repeat with remaining whipped egg whites until all are incorporated into the batter. Batter will be lighter in color and very fluffy. 
8. Bake: Pour into your pan and bake at 325 degrees F for 22-25 minutes, or until the top is golden brown and a toothpick inserted in the center comes out clean.
9. Remove from the oven and let cool. Run a sharp knife around the edge of the cake helping it to separate from the side of the pan.
10. Transfer. Release the springform pan sides or gently flip the cake and move to a cooling rack.
11. Cool completely, then decorate with optional lemon glaze. Transfer to a serving platter.

Lemon Glaze

1. Sift the powdered sugar into a medium bowl.
2. Add the lemon juice starting with 3 tablespoons, adding more as needed to get a thick glaze. Whisk until smooth. It should be quite thick, but still drip off the spoon.

Icing The Cake

1. Wait to glaze your cake until it has cooled down completely (roughly 30 minutes) and comes to room temperature – this way, you’ll be able to better control the drips and make them pretty!
2. Spread the icing, starting in the middle of the cake, spreading it to the outsides in an even layer. Add more glaze along the edges to allow the glaze to drip down the sides of the cake for a fun and pretty drip.
3. I recommend making the glaze right before you need it and using it all at the same time. If you try to store it, it will harden and will no longer be able to pour.