How to Make It
In a large bowl, whisk the crème fraîche with the eggs, half-and-half, salt and pepper. Add the bread, scallions and the 1/4 cup of capers and mix well. Scrape into a 9-by-13-inch baking dish, cover with plastic wrap and let soak for 1 hour.
Preheat the oven to 375°. Bake the strata for 45 to 50 minutes, until puffed and the top is golden. Let stand for 10 minutes. Scatter some salmon on top and garnish with red onion and capers. Serve, passing more salmon at the table.