Raspberry jam is traditional for a linzertorte, but any seedless jam works well in this dessert.
Preheat oven to 350 degrees. In a small bowl, combine flour, almonds, cinnamon, baking powder, and salt; set aside.
In the bowl of an electric mixer fitted with the paddle attachment, cream butter and brown sugar until smooth. Beat in egg. Gradually add flour mixture, beating on low speed just until the mixture comes together to form a dough.
Turn out dough onto a lightly floured work surface. Remove one-third dough, and set aside. Roll out remaining dough to 1/8 inch thick. Fit into a 9-inch square or round tart pan, pressing into corners and sides. Using a paring knife, trim the dough flush with edges of pan, and patch any holes or tears with extra dough.
Roll out reserved dough into a rectangle at least 13 inches long and 1/8 inch thick. Cut lengthwise into 1/2-inch-wide strips. Transfer to a baking sheet; refrigerate, along with shell in pan, 30 minutes.
Over medium heat, melt the raspberry jam in a small saucepan, stirring occasionally until smooth. Remove from heat, strain through a fine sieve, and let the jam cool slightly.
Remove tart pan from refrigerator, and pour jam into shell. Remove dough strips from refrigerator, and arrange over the top in a lattice pattern. Trim the excess dough, and press ends into edge of shell to adhere. Bake until pastry is golden brown and jam is bubbling, 30 to 35 minutes. Transfer to a wire rack to cool. Dust top with confectioners' sugar, and serve.
Before pouring into shell, strain jam. Place it over low heat, and pass it through a fine sieve. Then let it cool.