To make the crust:

1. Place the flour, sugar, and salt into the bowl of a food processor. Pulse 3-4 times to combine.
2. Scatter the small pieces of butter onto the flour mixture and pulse 10 times in 1-second intervals. It will look like coarse crumbs.
3. Mix the apple cider vinegar with the water.
4. Add 5-6 tablespoons of the water & cider mixture from the tube and process until the dough comes together, 7-10 seconds. If it doesn’t come together add more water, 1 tablespoon at a time, until it does.
5. Transfer the dough onto a sheet of plastic wrap and flatten into a 4-inch disk. Wrap it tightly in plastic and refrigerate for an hour (or overnight).

To make the plum tart:

1. Preheat the oven to 375 degrees.
2. Take the pie dough from the fridge and let it sit in room temperature for 10 minutes.
3. Unwrap and transfer it onto a lightly floured kitchen counter. Roll it into a 12-inch circle that is 0.15-inch thick. Trim the edges to a clean circle with a pastry cutter.
4. Transfer the dough into a baking sheet lined with parchment paper. At this point, if your dough is too soft, feel free to place it in the fridge to cool for 5-10 minutes. This way it will be easier to work with.
5. Sprinkle the dough with 3 tablespoons of sugar, leaving 1-inch border from the outside.
6. Arrange the sliced plums overlapping onto each other on top of the dough, the way it is shown in the picture. It will be much easier if you start from the middle. For this recipe, I used 11 slices of plums in the center, 31 slices of plums in the second layer (surrounding the center), and 54 slices of plums in the outer layer.
7. Sprinkle it with 2 tablespoons of sugar. *read note 1
8. Roll the outer edges of the dough towards the plums. Brush the edges with the melted butter.
9. Bake the plum galette for 40-45 minutes, making sure to rotate the pan half way through the baking process for even baking.
10. In the mean time, make the glaze. Place the rest of the sliced plums into a small saucepan, add ½ cup sugar, and let it sit on the counter for 10 minutes. You will see that some of the sugar will melt with the help of the juices in the fruit.
11. Heat it in medium heat or until all the sugar is fully melted, for 10-12 minutes. Pass it through a strainer and discard the pulp. Place the glaze into a small bowl.
12. Remove the galette from the oven and let it cool for 5 minutes. Spoon or brush the top of the plums with the glaze, cut into slices, and serve.*read note 2