How to Make It
Put the eggs in a large saucepan, cover with cold water and bring to a rolling boil. Cover tightly and remove from the heat. Let stand for 12 minutes.
Fill a medium bowl with ice water. Pour out the water from the saucepan and shake the pan gently to crack the egg shells. Transfer the eggs to the ice water to cool, then pat the eggs dry. Peel the eggs and halve each one lengthwise. Slice a thin sliver from the bottom of each egg half to keep it steady.
In a small bowl, combine the radishes with the crème fraîche, lemon zest and a pinch each of salt and pepper. Spoon the radishes onto the eggs and top with a small dollop of salmon caviar.
In a small skillet, cook the butter over moderate heat until lightly browned and fragrant, about 5 minutes. Season with salt and spoon a small drizzle over the caviar. Serve right away.