Adapted from San Sebastián native Alejandro Pacheco Gurrachaga’s family, this recipe is a version of txangurro a la donostiarra, a locally popular dish created by a Basque chef in the early 20th century.
6 small or 3 large tomatoes (1¾ lb.)
1 tbsp. plus 1 tsp. extra-virgin olive oil
1 3⁄4 cups finely chopped yellow onion (from 2 small onions), divided
2 pinches kosher salt
3⁄4 tsp. Sugar
3 tbsp. unsalted butter, divided
14 oz. fresh crabmeat (about 2 packed cups), from about 2–3 large cooked buey de mar or Dungeness crabs
1⁄2 cup coarse dried bread crumbs
3⁄4 tsp. brandy
Bread, for serving (optional)
Slice a large X through the bottom skin of each tomato. In a large pot of heavily salted, boiling water, add the tomatoes and let cook until the cut skins start to pull away, about 1 minute. Remove and let cool slightly, then peel away and discard the skins. Core and seed the tomatoes, then finely dice the flesh. Set aside.
Set a rack in the top third of the oven and preheat to broil. In a large skillet over medium heat, heat 1 tablespoon olive oil. Add 1½ cups of the onion and a pinch of salt and cook, stirring occasionally, until softened but not browned, 6–7 minutes. Add the tomatoes, a pinch of salt, 1 tablespoon of butter, and the sugar; cook, stirring, until some of the tomato juices have evaporated, 6–8 minutes more. Turn off the heat.
Transfer the onion mixture to a large bowl. Add the crabmeat, 2 tablespoons of the bread crumbs, the remaining teaspoon olive oil, and the brandy; stir gently to combine.
Transfer the crab mixture into a clean, empty shell from the crab body set on a baking sheet (pack the mixture or use two shells as needed to fit), or transfer to a medium (32-ounce) baking or soufflé dish. Sprinkle the top with the remaining ¼ cup onion, then the remaining bread crumbs. Cut up the remaining butter into small pieces and distribute on top.
Broil until the crumbs are browned and crispy, 5–8 minutes. Serve warm with bread if desired.