In a food processor, pulse the flour and salt. Add the butter and pulse until it is the size of small peas. Sprinkle the ice water over the mixture and pulse until the pastry starts to come together. Transfer the pastry to a work surface and knead gently a few times until thoroughly blended. Divide the pastry in half and flatten into disks. Wrap the pastry in plastic and refrigerate until chilled, about 1 hour.
Preheat the oven to 400°. Line a large baking sheet with parchment paper. On a lightly floured work surface, roll out 1 of the pastry disks 1/8 inch thick. Using a 5-inch plate as a guide, cut out 4 rounds and transfer to the prepared baking sheet. Repeat with the second pastry disk. Refrigerate the rounds until firm, about 10 minutes.
Arrange the pineapple, mango and banana slices on the pastry rounds and scatter the strawberries and blueberries on top. Bring the pastry edges up and around the fruit, pinching firmly to form a pleated rim on each tart. Refrigerate the tarts until firm, 10 minutes.
Brush the tarts with the melted butter and sprinkle with sugar. Bake for 35 minutes, until the pastry is browned and the fruit is bubbling. Let the tarts cool on a rack. Serve warm or at room temperature with crème fraîche.