In a bowl sift together all purpose flour and baking powder. Set aside.
Using your stand or hand mixer, beat the room temperature butter till it becomes soft and creamy.
Add sugar gradually and cream the butter and sugar together till it becomes smooth and creamy.
Add in the eggs, one by one and beat the whole mixture till it comes to a smooth consistency.
Add in the vanilla extract and mix.
Now add the flour and baking powder slowly into wet ingredients.
Beat the mixture for 2 minutes till it looks smooth.
Pour the batter into a 8 x 8 square cake pan.
Bake the cake at 325 F for 40 minutes.
Take out of the oven and allow it to cool for 10 minutes and then cut into thin slices. [Cut the cake once from the center and then into slices] The rusks will be soft at this point of time.
Now reduce the temperature of the oven to 300 F.
Arrange the slices on a baking tray, leaving some space between them.
Put the tray into the oven and bake at 300 F for 10 minutes.
After 10 minutes, take out the tray and flip the rusks to bake the other side.
Put the tray back into the oven and bake again for 10 minutes.
Each side should appear dark golden brown after the 2nd bake.
Allow the cake rusks to cool completely.
Once cooled, the rusks will be crunchy and crispy. Store them in airtight container.