Heat oven to 300 degrees.
Brush an 8-inch fluted tart pan with butter. In a bowl, mix together remaining butter with cane sugar, vanilla, and salt. Add flour and mix until just combined.
Press dough into prepared pan and chill in the freezer, 15 minutes.
Sprinkle the top with raw sugar and bake until golden, about 45 minutes.
Remove from oven, let cool slightly, then carefully remove from pan. Cut into 12 wedges and arrange on a parchment-lined baking sheet, leaving about 1 inch between each wedge.
Bake until crisp, about 15 minutes more. Let cool completely.