Pat the salmon dry with paper towels. Run clean fingers over the flesh and remove any pin bones with clean tweezers or fish pliers. Leave the skin on; it makes slicing the cured salmon easier.

In a small bowl, mix the kosher salt, sugar, and black pepper. Scatter about one-third of the dill in the center of a rimmed dish or small baking pan just large enough to hold the salmon.

Sprinkle half of the salt mixture over the dill. Place the salmon skin-side down on top, then cover the flesh evenly with the remaining salt mixture. Pack the remaining dill over the salmon.

Cover the salmon tightly with plastic wrap or place it in a large resealable bag. Set a second small pan or plate on top and weigh it down with a few cans. Refrigerate for 36 to 48 hours, turning the salmon over once about halfway through the curing time. Keep it refrigerated throughout.

To make the dill mustard sauce, whisk the Dijon mustard, whole-grain mustard, honey, apple cider vinegar, and oil until smooth and slightly thickened. Stir in the chopped dill. Refrigerate until ready to serve.

Unwrap the salmon and discard the dill and liquid. Briefly rinse the surface under cold running water, then pat very dry. Place the salmon skin-side down on a cutting board. Holding a sharp slicing knife at a low angle, cut very thin slices from the wide end, leaving the skin behind.

Serve chilled with the dill mustard sauce. For an easy lunch or appetizer platter, add rye bread or crackers, cucumber slices, lemon wedges, pickled red onions, and greens.