Cherry thumbprint Christmas cookies - Click Americana

Ingredients

• 1/4 cup butter
• 1/4 cup sugar
• 1 egg yolk
• 1/2 teaspoon vanilla
• 1 tablespoon lemon juice
• 1 tablespoon grated lemon peel
• 1 tablespoon grated orange peel
• 1 cup plus 2 tablespoons all-purpose flour
• 1/2 teaspoon salt
• 1 egg white, slightly beaten
• 1/2 cup finely-chopped walnuts (or pecans)
• 1/2 cup red and green candied cherries, halved