Heat oven to 325 degrees. Brush an 11-by-17-inch baking pan with butter, line with parchment, and butter again; set aside. Whisk together milk, eggs, 1 cup honey, and the vanilla in a medium bowl.Advertisement
Place flour, sugar, baking powder, and salt in bowl of electric mixer fitted with paddle attachment. Mix on low until combined. Add butter, half the milk mixture, and lemon zest. Increase speed to medium, and beat for 1 minute. Scrape the sides of bowl, and add remaining milk mixture in 2 batches, beating on medium for 1 minute after each addition.
Pour batter into the prepared baking pan, and smooth the surface with a spatula. Bake for 30 minutes, or until golden brown and cake springs back when gently pressed in the center.
Heat remaining 1/2 cup honey in a small saucepan, and brush onto warm cake. Cool completely in the pan on a wire rack, and then refrigerate until firm.