Preheat oven to 325°F. Grease and flour an 11-inch tart pan with a removable bottom. Cream together butter, powdered sugar, vanilla and salt with an electric mixer until light and fluffy. Add flour and polenta, and mix just until blended. Scrape dough into prepared pan. Use floured fingers to press dough evenly into pan. Sprinkle center with almonds, and press almonds into dough. Bake 35 to 45 minutes, until golden brown. Let cool, and remove tart shell from pan. Cut into wedges and top each piece with Caramelized fruit, a dollop of creme fraiche or sour cream and a sprinkle of almonds.
Caramelized fruit: 4 firm red pears 1 teaspoon fresh lemon juice 1/2 cup sugar 1 cup canned sweet cherries, well drained
Peel pears, and cut each one into 12 wedges, discarding cores. Toss pears in lemon juice. Place sugar in a large skillet, and turn heat to high. Let sugar caramelize, supervising closely and swirling pan occasionally for even color. When the caramel is deep golden brown, add pears and cherries, and stir gently, coating with caramel. Cool slightly.
Tip: Instead of using this shortbread dough as a tart crust, you may also use it for slice-and-bake cookies. After mixing, refrigerate the dough until firm. Use floured fingers to shape it into a log, roll it in sliced almonds, wrap it in plastic, and refrigerate it again until firm. Then, cut the log into slices, and place them on a greased baking sheet. Bake in a preheated 325°F oven for 10 to 15 minutes, until golden brown.