Preheat the oven to 230°C (approximately 445°F). preheat. The financier molds churning well.
Place the butter in a saucepan and set over medium heat. Melt the butter until it starts to foam, turn light brown, and smell nutty. Allow the butter to cool to room temperature.
In a large mixing bowl, whisk the egg whites to break them up. In a separate bowl, sift the icing sugar with the almonds, flour and lemon zest. Add the butter and egg white to the flour mixture and fold everything together.
Fill each financier mold halfway with the batter. Use the hilt of a wooden spoon to shape 3 small wells in each portion of batter and fill them with raspberry jam. Bake for 5 minutes in the preheated oven. Reduce the temperature to 200°C (approximately 390°F) and bake for an additional 5 minutes. Turn the oven off and let the cakes sit in the oven for another 5 minutes.
Remove the financiers from the oven and allow to cool slightly. Remove from the molds while still warm.
Serve dusted with powdered sugar.