Preheat the oven to 350 degrees F. Butter an 8 1/2- by 4 1/4- by 2 1/2-inch light-colored loaf pan.
Sift together the flour, baking powder and salt into a medium bowl. Combine the melted butter, sugar, yogurt, oil, zest, vanilla and eggs in a large bowl and whisk until well blended. Gradually whisk in the dry ingredients. Transfer the batter to the prepared pan.
Place the pan on baking sheet on the middle rack and bake until the cake begins to pull away from the sides and a tester inserted into the center comes out with a few moist crumbs attached, about 50 minutes. Cool the cake in the pan on a rack for 5 minutes before unmolding. Cut around the sides of the pan to loosen the cake, and then turn the cake out onto the rack. Turn the cake upright on the rack and cool completely.
Stir together the marmalade and liqueur in a small saucepan over medium heat until the marmalade melts. Brush the hot mixture over the top of the cake. Let the glaze cool and set. Cut the cake crosswise into slices.