Step 1

Look for tins labeled “mackerel fillets” or “mackerel,” which typically contain boneless, skinless fillets, versus tins labeled “small mackerel,” which often contain small fish with the skin and bones intact. You may substitute trout, unsmoked mackerel, or good-quality oil-packed tuna. Serve with a salad for a light meal.

Step 2

Combine 1½ teaspoons lemon juice, sugar, and salt in small bowl and microwave until mixture is steaming and sugar and salt are dissolved, 10 to 20 seconds. Add radishes and chopped dill and stir to coat. Set aside. In small bowl, stir cream cheese, shallot, Worcestershire sauce, hot sauce, and remaining 2 teaspoons lemon juice until well combined.

Step 3

Heat 12-inch skillet over medium heat until hot, about 2 minutes. While skillet heats, transfer radishes to paper towel–lined plate to drain. Spread 1 side of each piece of bread with 1½ teaspoons butter. Cook bread butter side down in skillet until evenly browned, 3 to 5 minutes.

Step 4

Transfer bread browned side down to cutting board. Spread each piece evenly with cream cheese mixture. Break mackerel into flakes and arrange over cream cheese mixture. Drizzle each tartine with 1 teaspoon reserved oil. Sprinkle with pepper. Arrange radishes and dill fronds on top and serve.