Heat the oven to 350 degrees Fahrenheit. Line 2 large baking sheets with butter paper.
Using an electric mixer, beat together the butter, brown sugar, and brown sugar. Add the peanut butter and eggs and mix until combined.
In a separate bowl, add the baking powder, baking soda, salt, and flour (sift the flour once). Add to peanut butter mixture and blend until combined.
Shape the dough into 1-inch balls, place the balls 3 inches apart on the prepared baking tray, and flatten them in a criss-cross pattern with a fork.
Bake for 8-9 minutes until the cookies begin to turn golden from the base. Remove from the oven and let cool for 5 minutes, then transfer to a wire rack.