Recipe

Make Crust

1. In large bowl, whisk together flour, sugar and salt. Add butter and toss to coat. Using hands, smash butter between palms and fingertips, mixing it into flour and creating long, thin, flaky, floury, buttery bits. Once most of butter is incorporated and no large chunks remain, dump flour mixture onto work surface.
2. In measuring cup, combine vinegar and ice water and drizzle it over flour-butter mixture. Run fingers through mixture like running fingers through hair to evenly distribute water through flour, until dough starts coming together.
3. Knead dough to gather up any dry bits from bottom and place on top to be incorporated. You will be tempted to add a tablespoon or two more water — resist if you can! Add only if you must.
4. Once you’ve got a shaggy mass of dough (it will not be smooth and it certainly will not be shiny), knead once or twice more and divide in half. Pat each piece into flat disc about 1″ thick. Wrap each disc individually in plastic wrap and refrigerate at least 2 hours.

Cook Onions

1. In large pot, heat olive oil over medium-low heat. Add all but one handful of onions and season with salt and pepper. Cook, stirring occasionally, until onions are deeply caramelized, totally softened, almost jammy, about 90 minutes (if you notice them getting a little dark, especially in the centre of the pot, add a splash of water and reduce heat). Caramelized onions take an annoying, painstakingly long time. Consider this a meditation in patience. Taste onions and season with salt and pepper. Remove from heat to cool slightly.

Make Tart

1. Preheat oven to 425F and line sheet pan with parchment paper.
2. On lightly floured work surface, roll out dough to 14″ round or 10″ x 14″ rectangle and transfer to lined pan. Spread caramelized onions on top, leaving 2″ border all around. Scatter with anchovies (I avoid traditional crisscross pattern, but you do you) and raw onions, then fold crust up around edges.
3. Beat egg with teaspoon of water, then brush crust with egg wash. Sprinkle with flaky salt and bake until crust is deeply browned and onions are even more caramelized, 40 to 45 minutes.
4. Let tart cool slightly before scattering with parsley, sprinkle of red pepper flakes and squeeze of lemon.