Put racks in upper and lower thirds of oven and preheat oven to 350°F. Brush molds with melted butter.
Sift together flour and baking powder into a large bowl, then whisk in zest.
Scrape seeds from vanilla bean into another bowl with tip of a paring knife (reserve pod for another use). Add sugar and rub together until vanilla is well dispersed, then whisk in eggs, milk, honey, and remaining 1 3/4 sticks melted butter. Fold into flour mixture until just combined.
Spoon a rounded tablespoon of batter into each mold, filling it about two-thirds full. Bake (with 2 pans on one rack), switching position of pans halfway through baking and rotating 180 degrees, until golden around edges and a wooden pick or skewer inserted into center of a madeleine comes out clean, 10 to 12 minutes total.
Turn out madeleines onto a rack and serve slightly warm.