In a mixing bowl, combine flour, sugar, and salt. Add cold butter and mix until the dough resembles coarse crumbs.
Add ice water, one tablespoon at a time, mixing until the dough comes together. Form into a disk, wrap in plastic, and chill for 30 minutes.
Preheat the oven to 375°F (190°C) and grease a tart pan.
Roll out the chilled dough on a floured surface and press it into the tart pan.
Arrange the sliced apples in overlapping concentric circles on the tart crust.
Sprinkle with brown sugar and cinnamon, then brush with melted butter.
Bake for 35-40 minutes, or until the apples are tender and the crust is golden.
In a small saucepan, heat the apricot jam and water until melted, then brush over the warm tart for a glossy finish.
Let the tart cool slightly before serving.