Simplify the following text for a Grade 7 native English-speaking person.
Original: The invention of baking powder and other chemical leavening agents during the 19th century substantially increased the flexibility of this traditional pound cake by introducing the possibility of creating lighter , fluffier cakes using these traditional combinations of ingredients , and it is this transformation that brought about the modern butter cake .
Simplified: This was the first butter cake . The invention of baking powder during the 19th century made it possible to have lighter , fluffier cakes using these same ingredients , making the modern butter cake .