Prepare the Egg Whites:

1. Preheat your oven to 350°F (175°C).
2. In a stand mixer or using a hand mixer, beat the egg whites with cream of tartar on high until foamy.
3. Gradually add ⅓ of the sugar and continue beating until firm peaks form. Set aside.

Prepare the Egg Yolk Mixture:

1. In a large bowl, combine egg yolks, the remaining sugar, salt, water, honey, and vanilla extract. Beat on high until the mixture is pale yellow and fluffy, creating ribbons when dropped from the whisk.
2. Gently fold in half of the beaten egg whites into the egg yolk mixture.

Combine Ingredients:

1. Sift cake flour, matcha powder, and baking powder into the egg yolk mixture in three parts, gently folding after each addition.
2. Incorporate the vegetable oil by mixing a small portion of the batter with the oil before adding it back to the mixture. Fold in gently.
3. Fold in the remaining egg whites until the batter is well combined and fluffy.

Bake:

1. Line two 6-inch cake pans with parchment paper.
2. Pour the batter evenly into the pans, and tap the pans gently to remove any large air bubbles.
3. Bake for 27-30 minutes, or until a toothpick inserted into the center comes out clean.
4. Remove the cake from the oven and allow it to cool completely on a wire rack before slicing or layering.