Step 1

Place raisins in a small bowl and cover with boiling water; set aside for 30 minutes.

Step 2

Meanwhile, heat oil in a large skillet over medium heat. Add onions and cook, stirring often, until the onions are softened and beginning to color, 5 to 10 minutes. Cover, reduce heat to medium-low, and continue cooking, stirring occasionally, until the onions are golden brown, 15 to 25 minutes more.

Step 3

Drain and chop the raisins; add to the onions along with capers, dill, pepper and salt. Cook uncovered, stirring, for 5 minutes. Transfer to a bowl and let cool for at least 30 minutes.

Step 4

Top each slice of bread with 1 tablespoon onion spread and 1 shrimp.