Preparation

The Mixing Bowl-- Preheat oven to 350°F with rack in middle. Butter and flour a 9- by 5-inch loaf pan. Whisk together flour, poppy seeds, baking powder, and salt. Scrape seeds from vanilla bean with tip of a paring knife into a bowl, then add butter and sugar and beat with an electric mixer at medium-high speed until pale and fluffy, about 3 minutes. Add eggs 1 at a time, beating well after each addition. At low speed, add flour mixture in 3 batches, alternating with half-and-half, beginning and ending with flour, and mixing until just incorporated. Spoon batter into loaf pan, smoothing top.

Bake it-- Bake until golden-brown and a wooden pick inserted into center comes out with crumbs adhering, 1 to 1 1/4 hours. Cool in pan 30 minutes. Run a knife around edge of cake to loosen, then invert cake onto a rack. Cool completely, right side up.