1. Preheat oven to 325ºF; line a baking sheet with foil. Put almonds in a small heavy skillet over medium heat and toast, stirring and watching carefully, until golden brown, about 4 minutes. Transfer to a plate to cool.
2. In a bowl, using an electric mixer on medium-high speed, beat butter, sugar, zest and salt until light, about 3 minutes. Reduce speed to low and mix in flour. Mix in cranberries and almonds.
3. Press dough into a 9-inch tart pan with removable bottom or a 9-inch springform pan. Prick all over with a fork. Use a sharp paring knife to cut into 12 wedges. Set pan on top of baking sheet. Bake until golden and firm at edges but still a little soft in center, about 30 minutes. Recut into wedges while still warm. Let cool completely in pan on a wire rack. Remove pan sides and separate wedges. Drizzle with melted white chocolate, if desired, and serve.