Preheat your oven to 320°F (160°C) and line a rectangular baking pan with parchment paper.
In a mixing bowl, sift the flour to remove any lumps. Set it aside.
In another large mixing bowl, combine the eggs and sugar. Using an electric mixer, beat them together on medium-high speed for about 8-10 minutes until the mixture becomes pale, thick, and creamy.
Gradually add the sifted flour to the egg-sugar mixture. Gently fold it in using a spatula until well combined, making sure not to overmix.
In a separate small bowl, mix the honey, milk, and vanilla extract. Add this mixture to the batter and gently fold it in until fully incorporated.
Pour the batter into the prepared baking pan and give it a few taps on the counter to remove any air bubbles.
Bake in the preheated oven for approximately 50-60 minutes or until the top turns golden brown and a toothpick inserted into the center of the cake comes out clean.
Once baked, remove the cake from the oven and let it cool in the pan for about 10 minutes. Then, transfer it to a wire rack to cool completely.
Once cooled, slice the Castella cake into desired portions and enjoy!
