Preheat oven to 350degrees. In a large bowl, whisk flour, sugar, orange zest and baking powder. In another bowl, whisk eggs, milk and oil until blended. Add to flour mixture; stir just until moistened., Shape into a 6-in. round loaf on a greased baking sheet. Brush top with egg yolk; sprinkle with coarse sugar. Bake 45-50 minutes or until a toothpick inserted in center comes out clean. Cover top loosely with foil during the last 10 minutes if needed to prevent overbrowning. Remove from pan to a wire rack; serve warm.