For the oatmeal cookies, preheat the oven to 150 °C. Beat butter and brown sugar until creamy. Stir in egg.
Mix oats, almonds, baking powder and lemon zest. Gradually stir into butter-egg mixture. Wrap dough in plastic wrap and chill for about 30 minutes.
Roll out the dough to about 5 mm thick and cut out circles and bake the oatmeal cookies for about 10 minutes.