I often feel that the beauty of a pound cake is in it's very simplicity, so I've never gone too wild with the flavor combinations, but by substituting the lemon juice in the following recipe for whatever liquid you have on hand (milk, yogurt, sour cream, any flavor of juice, or liqueur. You can also add any flavor of extract you wish, brown sugar instead of white, chopped nuts, dried fruit, etc.
Lemon Orange Pound Cake
(Adapted from Moosewood Restaurant New Classics)
2 cups unsalted butter, at room temperature
3 cups sugar
2 tsp pure orange extract
4 cups unbleached white pastry flour or cake flour
1/2 cup lemon juice
2 tsp baking powder
zest from 1 or 2 lemons
1 tsp pure orange extract
2 to 3 Tablespoons orange juice
1-1/2 cups confectioners' sugar
zest from 2 or 3 lemons
Preheat the oven to 350 deg. Butter and flour a 10-inch Bundt pan (be sure that the pan will hold at least 12 cups -- if it is smaller, put a few cups of batter into a miniature loaf pan or make it into a few muffins).
With an electric mixer, cream the butter and sugar. Beat in the orange extract and the eggs. Add 2 cups of the flour and beat well. Add the lemon juice and zest and beat. In a separate bowl, or measuring cup, stir the baking powder into the remaining 2 cups flour. Add to the batter and beat well.
Spoon the batter into the prepared Bundt pan and bake until the cake pulls away from the sides of the pan and a knife inserted in the center comes out clean, about 60-75 minutes. Cool the cake in the pan on a rack for 10 minutes. Invert onto a serving plate, leaving the pan on top so the cake holds it's shape. Cool for another 10 or 20 minutes.
Meanwhile, prepare the glaze. Stir the orange extract and the lemon juice into the sugar with a fork, adding the lemon juice a tablespoon at a time; use just enough to produce a thick, smooth mixture. Spread the glaze over the cake with a pastry brush while the cake is still warm, or drizzle it on in a lazy pattern.