Position rack in center of oven and preheat to 350 degrees.

Generously butter an 8 1/2x4 1/2x2 1/2-inch metal loaf pan.

Sift together the flour, baking powder, and salt into a medium bowl.

Combine yogurt, sugar, eggs, lemon peel, and vanilla in a large bowl and whisk until well blended.

Gradually whisk in the dry ingredients. Using a rubber spatula, fold in the oil. Transfer batter to a prepared pan.

Place the pan on a baking sheet on the middle rack and bake until 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 cake, and then turn the cake out onto the rack.Turn the cake upright on the rack and cool completely.

Stir marmalade and 1 teaspoon of water together 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. Serve it on it's own or with whipped cream and fresh berries.

(Can be made 1 day ahead. Wrap and store at room temperature.)