- 1 1/2 pounds plum tomatoes (about 10), halved lengthwise
- 1/4 cup olive oil
- Kosher salt
- 1/2 teaspoon fenugreek seeds
- 1/4 teaspoon cumin seeds
- 1/4 teaspoon black peppercorns
- 1/2 cup mayonnaise
- 4 (3/4-inch-thick) slices country-style bread
- 3 tablespoons olive oil, divided
- 1 small fennel bulb, quartered lengthwise, very thinly sliced
- 1 tablespoon coarsely chopped dill
- 1 tablespoon coarsely chopped parsley
- 1 tablespoon fresh lemon juice
- Kosher salt
- 2 (4.2-ounce) cans oil-packed sardines, drained, pin bones removed
- A spice mill or a mortar and pestle
- Preheat oven to 500°F. Toss tomatoes with oil on a rimmed baking sheet to coat. Roast until skin is blackened and tomatoes are very soft, 20–25 minutes. Pass tomatoes through finest disk of a food mill or a coarse-mesh sieve into a small saucepan; season with salt. Bring to a simmer over medium-low heat, stirring often, and cook until you have about 1/2 cup tomato purée. Let cool.
- Meanwhile, toast fenugreek, cumin, and peppercorns in a dry small skillet over medium heat, tossing often, until fragrant. Let cool and finely grind in spice mill or with mortar and pestle.
- Mix tomato purée, spice mixture, and mayonnaise in a bowl; season with salt.
- Prepare a grill for medium-high heat. (Alternatively, heat a grill pan over medium-high.) Brush both sides of bread with 2 Tbsp. oil total and grill until lightly charred, about 2 minutes per side.
- Toss fennel, dill, parsley, lemon juice, and remaining 1 Tbsp. oil in a medium bowl; season with salt. Spread tomato mayonnaise over toast and top each with a few sardines and some fennel salad.
- Tomato mayonnaise can be made 5 days ahead. Cover and chill.