Bake these brandy-spiked bars up to two days ahead, and cut just before serving.
Preheat oven to 350 degrees. Brush a 9-by-13-inch baking pan with butter. Line with parchment paper, leaving a 2-inch overhang on two sides; butter paper, and set aside. In a medium bowl, whisk together flour and salt; set aside.
In a medium saucepan, heat brandy until simmering. Remove from heat, and stir in fruit; cool to room temperature. Toss brandied fruit with 1 cup flour mixture; set aside.
Using an electric mixer, beat butter and brown sugar until light and fluffy. Add eggs, one at a time, beating well after each addition; mix in vanilla. With mixer on low, add remaining flour mixture; mix just until combined. Fold in fruit mixture; transfer batter to prepared pan, and smooth top.
Bake until a toothpick inserted in center of cake comes out clean, 45 to 50 minutes. Cool in pan for 1 hour. Using paper overhang, lift out of pan; transfer to a wire rack to cool completely (still on paper). Invert fruitcake, and peel off paper; flip upright, and cut into 24 diamonds with a serrated knife. Dust with confectioners' sugar, if desired.
Use an array of dried fruits, such as raisins, apricots, cranberries, dates, prunes, cherries, or pineapple for a traditional fruitcake flavor. Pick 2 or 3 of your favorites to create your own version.