Sift together flour, baking powder, and salt in a bowl.

In a separate bowl, cream together butter (or margarine) and peanut butter with the sugar until the mixture is light and fluffy.

Add the egg and crushed pineapple to the creamed mixture.

Gradually stir in the dry flour mixture until just combined.

Form the dough into oblong shapes, using about 1 heaping teaspoon of dough for each cookie.

Place the cookies on a baking sheet.

Bake in a preheated 375 degree oven for approximately 10 minutes, or until golden brown.