Butter a 20-cm (8-inch) square cake pan. Line the bottom and two opposing sides with parchment paper, letting the paper hang over the two sides.
In a bowl, combine the flour, baking powder and salt. Set aside.
In a separate bowl, cream the butter and brown sugar with an electric mixer. Add the egg and beat until the mixture is smooth. With the mixer on low speed, add the dry ingredients, alternating with the milk. Using a wooden spoon, gently fold in the almonds and spread the mixture in the cake pan. Refrigerate for 15 minutes.
With the rack in the middle position, preheat the oven to 170°C (325°F).
In a bowl, combine the cranberries, juice and sugar. Spread over the batter, gently pressing the cranberries into the bottom layer. Sprinkle with the almonds. Bake until a toothpick inserted in the centre comes out clean, 40 to 45 minutes. Let cool to room temperature. Grasp the ends of the parchment paper and lift the pastry out of the pan. Cut into 5 x 2.5-cm (2 x 1-inch) bars.