A light, airy, and elegant dessert featuring a delicate raspberry flavor and a fluffy texture.
Preheat the oven to 400°F (200°C). Butter and sugar six 6-oz ramekins.
In a blender or food processor, puree raspberries until smooth. Press the puree through a fine-mesh sieve to remove the seeds. Set aside.
In a saucepan, melt butter over medium heat. Add flour and whisk constantly for 1-2 minutes to make a roux.
Gradually whisk in milk and 1/2 cup of granulated sugar. Cook, stirring constantly, until the mixture thickens and comes to a boil.
In a bowl, whisk egg yolks. Slowly pour the hot milk mixture into the yolks, whisking constantly to temper them.
Whisk the tempered egg yolk mixture back into the saucepan. Stir in the raspberry puree and lemon zest. Remove from heat and let cool slightly.
In a large bowl, beat egg whites until soft peaks form. Gradually add the remaining 1/4 cup of granulated sugar and continue beating until stiff, glossy peaks form.
Gently fold one-third of the egg white mixture into the raspberry batter to lighten it. Then, fold in the remaining egg whites until just combined.