Gravlax With Caraway, Coriander, and Mustard-Dill Sauce
Kosher salt, 1 (2-pound; 900g) skin-on sushi-grade salmon fillet, pin bones removed by fishmonger, 1 teaspoon caraway seeds, 1 teaspoon coriander seeds, 40g kosher salt (about 4 tablespoons), plus more for washing salmon, 25g sugar (about 1 tablespoon)