12tablespoonscoldunsalted butter, cut into ½ inch cubes
1/3cupplus 1 teaspoon ice water
1teaspoonapple cider vinegar
Filling
3-4medium plumspits removed and thinly sliced
¼cupgranulated sugar
¾teaspoonground cinnamon
3tablespoonsall-purpose flour
3tablespoonscoldunsalted butter cut into tiny pieces
1egglightly beaten (to use as a glaze)
¼cupgranulated sugar for sprinkling
Instructions
Make Flaky Pastry
In a food processor, pulse both flours, salt, and butter until butter is the size of peas.
Add the ice water and vinegar all at once and pulse just until water is incorporated.
Pour the mixture into a medium bowl and gently gather into a ball. Wrap in plastic wrap and flatten into a 1 inch thick disk. Chill for 20 minutes.
Assembly
Preheat oven to 400° F.
On a lightly floured surface, roll out the pastry to a rough 12-14 inch circle.
In a small bowl, combine ¼ cup granulated sugar, cinnamon, and flour.
Scatter the sugar mixture all over the rolled out crust leaving 2 inches of the edge uncovered.
Arrange sliced plums on top of sugar mixture. Scatter tiny butter pieces all over the plums.
Using a pastry brush, brush border of crust with beaten egg.
Fold the edges of the tart up over the plums creating a 1½-2 inch border, pressing down gently. Transfer the tart to a large pizza pan covered with parchment paper.
Brush the edges of the tart with the beaten egg and sprinkle the entire tart, including the border, with the remaining ¼ cup sugar.
Bake the tart for 40-45 minutes or until golden brown and the plums are softened.
Serve the tart warm, cut into slices and topped with vanilla ice cream or whipped cream.