Heat 2 tablespoons butter in a large skillet over medium heat. Fry the tomato slices until browned, about 5 minutes. Season with salt and pepper and set aside.
Beat the eggs and sour cream together in a medium bowl and stir in the salmon and chives. Heat the remaining butter in small skillet over medium heat. Add the egg mixture and cook until lightly set and soft, about 2 minutes. Serve with the tomatoes and a croissant. Enjoy in Paris or while listening to Edith Piaf.