Step 1

Shingle bread slices and salmon in an 8-by-12-inch (3-quart) baking dish. Sprinkle with cheese. Whisk together eggs, creme fraiche, milk, dill, 1/2 teaspoon salt, and 1/4 teaspoon pepper; pour over bread. Cover and refrigerate at least 2 hours and up to 1 day.

Step 2

Preheat oven to 375 degrees with a rack in middle. Uncover and bake until cheese has melted and strata is puffed and golden, about 30 minutes. Let cool slightly, then serve, with capers, lemon wedges, and onion slices alongside.