Place sugar and lemon zest a bowl. Using your fingertips, rub sugar and lemon zest together until sugar is moist and fragrant. Add eggs and whisk until mixture is pale and thickens slightly, about 2 minutes. Whisk in honey and vanilla. Alternatively, this can be done in the bowl of an electric mixer fitted with the whisk attachment.

Gently fold in flour mixture in three additions; fold in melted butter until fully incorporated. Stir in milk. Batter should be smooth and shiny. Press a piece of plastic wrap against the surface of the batter; transfer to refrigerator and let chill at least 1 hour and up to 2 days.

Butter and flour a large madeleine pan. Spoon batter into madeleine pan; transfer to refrigerator for 1 hour.

Place a heavy, large baking sheet in oven; preheat oven to 400 degrees.