3/4cup+ 2 tbsp unsalted buttercut into small pieces
Finely grated zest of 3 limes
1/2cupfresh lime juicefrom about 5 limes
5kiwispeeled and sliced
Measure the flour, sugar, and salt into the bowl of a food processor and pulse a few times to combine. Sprinkle butter over top and pulse until the butter pieces are no bigger than lentils. In a separate bowl, whisk together the egg yolk (be sure to reserve the white for the next step!), vanilla, and water. Sprinkle over the flour mixture and pulse a few times until mixture starts to form large clumps. Dump onto a parchment-paper-lined counter and gently press the dough together until it is cohesive. Form into a disk shape, wrap up in the parchment paper and refrigerate at least 30 minutes (or up to 2 days).
Preheat oven to 375ºF. Roll the dough between two layers of parchment paper into a 12" circle and transfer to a 9 1/2" tart pan, gently pressing into bottom and up sides. Line with parchment paper and fill with pie weights (or dry beans). Blind bake the tart shell on the bottom oven rack for about 15 minutes, until it starts to look dry, then carefully remove pie weights and parchment. Continue baking until the crust is golden, 10 minutes longer. Lightly brush the inside with lightly-whisked reserved egg white (you won't need all of it) and continue baking for about 5 minutes more, until white is set shiny. Gently transfer to a wire rack and cool completely in the tart pan.
To make the curd, bring the sugar, butter, lime zest and juice to a simmer over medium heat. In a bowl, lightly whisk the eggs. Very slowly (a tiny bit at a time) stream about half the hot lime mixture into the eggs while whisking constantly, then slowly whisk this egg mixture back into the remaining lime mixture in the saucepan. Cook over medium-low heat, stirring constantly, until mixture thickens enough to coat the back of a spoon, about 5 minutes. Press through a fine-mesh sieve into a bowl, then chill completely (either by stirring it over an ice bath, or by refrigerating at least 2 hours).
When crust and lime curd are both cool, pour the curd into the crust and top with kiwi slices.