Bring a pot of salted water to a boil. Rinse the spinach, remove the thick stems, and add it to the boiling water. As soon as it returns to a boil, count two minutes and transfer it to cold water. Squeeze out the excess water using a colander, and set aside in the refrigerator.
Slice the salmon into fairly thin slices and set aside in the refrigerator.
In a mixing bowl, whisk together the eggs and crème fraîche. Season with salt and pepper to taste.
Coarsely chop the spinach, then strain it again through a fine-mesh sieve to drain it thoroughly. Add it to the filling, along with the salmon.
Preheat the oven to 220°C. Roll out the dough with a rolling pin and place it in a buttered pan. Prick the bottom with a fork, then pour the filling over it.