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  1. To make the crust: Place all of the ingredients except the vinegar in the bowl of a food processor. Pulse until the mixture looks like coarse meal. Add the vinegar and process until the mixture comes together.

  2. Turn the dough out onto a lightly floured work surface and fold it over on itself once or twice. Roll it into a 5" x 16" rectangle. Tuck the dough into a 4" x 14" tart pan with a removable bottom, pressing it into the corners and up the sides. Run a rolling pin across the top to trim the dough.

  3. Refrigerate the crust for 30 minutes while you preheat the oven to 425°F.

  4. Prick the crust all over with a fork, line it with foil or parchment, and fill with pie weights. Place the tart pan on a baking sheet and bake the crust for 12 to 15 minutes. Remove from the oven, remove the liner and weights, and return to the oven for 10 to 14 minutes, until the crust is golden brown all over. Remove from the oven and let cool to room temperature.

  5. To make the filling: Place all of the filling ingredients in the bowl of a food processor and process until smooth. Spread the filling in the cooled crust.

  6. To finish the tart: Cover the tart with folded slices of smoked salmon. Top with fresh parsley (or dill) and capers before serving.

  7. Store any leftovers, well wrapped, in the refrigerator for up to several days.