Generously butter 10-inch-diameter cake pan with high sides (or 7-1/2 x 11-1/2-inch cake pan with high sides (or 7-1/2 x 11-1/2-inch ovenproof glass baking dish).

Heat syrup, 1/4 cup butter, brown sugar and mace in heavy medium saucepan over low heat, stirring until sugar dissolves. Bring to boil. Pour into prepared pan. Sprinkle with pecans.

Position rack in center of oven and preheat to 350 degrees F. Sift flour, baking soda and salt into bowl. Using electric mixer, cream 1/2 cup butter in another bowl. Add 3/4 cup sugar and beat until light and fluffy. Beat in eggs 1 at a time, then beat 2 minutes. Blend in vanilla and lemon peel. Stir in flour mixture and yogurt alternately, beginning and ending with flour mixture. Fold in currants. Spoon batter atop pecan mixture, spreading gently to sides of pan. Bake until tester inserted in center comes out clean, about 55 minutes. Immediately invert cake onto rack set over sheet of waxed paper. Serve warm. Pass cream if desired.