Preheat oven to 350°F (175°C).

Sift cake flour, baking powder, and salt together three times to ensure even distribution and lightness.

Measure 2 cups of sugar and reserve 1/4 cup for later use.

In a large bowl, beat egg yolks and boiling water together until frothy.

Gradually add 1 3/4 cups of sugar to the egg yolk mixture and beat well until combined.

Add the sifted dry ingredients (flour, baking powder, salt), vanilla extract, and lemon extract to the egg yolk mixture.

Fold gently until just blended, being careful not to overmix.

In a separate bowl, beat egg whites until stiff peaks form.

Gradually add the reserved 1/4 cup of sugar to the beaten egg whites and continue beating until glossy and stiff.

Gently fold the sweetened egg whites into the other ingredients, ensuring they are evenly distributed without deflating the mixture.

Pour the batter into an ungreased angel food cake pan.

Bake for 1 hour, or until a toothpick inserted into the center comes out clean.

Once baked, let the cake cool completely in the pan before removing and slicing.