1. Preheat oven to 325°.
2. Beat butter with a mixer at medium speed until creamy. Add 1 cup sugar; beat well. Add eggs, 1 at a time, beating well after each addition. Beat in orange juice concentrate, citrus rinds, and vanilla.
3. Lightly spoon flour into dry measuring cups; level with a knife. Combine flour, baking powder, baking soda, and salt. Gradually add to butter mixture, beating well. Turn dough out onto a lightly floured surface; knead 5 or 6 times. Divide dough in half; shape each half into a 9-inch-long roll. Place rolls, 4 to 5 inches apart, on a baking sheet coated with cooking spray; flatten each roll to 1-inch thickness.
4. Brush dough with lemon juice; sprinkle evenly with 2 teaspoons sugar. Bake at 325° for 29 minutes. Place rolls on a wire rack; cool slightly. While rolls cool, wash any caramelized sugar from baking sheet, and dry thoroughly.
5. Cut rolls diagonally into 1/2-inch slices. Stand slices upright on baking sheet. Bake at 325° for 17 minutes. Remove cookies from baking sheet, and cool completely on wire rack.
Biscotti (bee-SKAWT-tee) are so named because they are "twice-baked." These firm, crunchy cookies are perfect for dunking in dessert wine or coffee.