For the cake:

Whisk egg yolk and eggs in a bowl fully. In another bowl beat egg whites, sugar and egg white powder to make a meringue, and add lemon zest. In a small pot heat milk, butter, salt and vanilla extract to boiling. Mix the whisked eggs with the meringue. Sift flour and almond cardamon tea powder into egg and meringue mixture. Then add boiled liquid and mix evenly. Spread in a half sheet pan with parchment paper. Bake at 180c for 18 minutes.

For almond cardamon tea paste:

Boil milk and almond cardamon tea in a small pot for three minutes, turn off the heat, let it rest for five minutes. Filter out the tea particles. Pour the milk back to the pot, add sugar and heat until the texture thickens. Add salt and store in a jar.

For almond cardamon tea extract:

Put the tea into the water and cook slowly until it boils, then seal and soak for 20 minutes, filter out the tea particles.

For the almond cardamon tea cream filling:

Mix all ingredients together. Spread it onto the cake and roll it, then set it in refrigerator at least two hours or overnight, dust with sugar and almond cardamon tea powder mixture(1:1), and use the leftover cream filling for decoration.