Preheat the oven to 175 degrees. Line the baking tray with baking paper. Beat the butter and sugar lightly. Mix in the egg. Mix the flour and baking powder with the butter mixture. Now roll the dough into little balls and place on the baking tray about 5 centimetres apart. Use your thumb or the stem of a ladle to make an indentation in each cookie. Fill the indentation with a little jam. Bake the cookies for about 10 minutes until light brown. When the cookies come out of the oven, you can top them off with little more jam.