½ pound unsalted margarine at room temperature
2½ cups granulated sugar
4 extra-large eggs at room temperature
⅓ cup grated lemon zest (6 to 8 large lemons)
3 cups all-purpose flour
½ teaspoon baking powder
½ teaspoon baking soda
1 teaspoon kosher salt
¾ cup freshly squeezed lemon juice
¾ cup pareve milk, or soymilk at room temperature
1½ tablespoons white vinegar
1 teaspoon pure vanilla extract
For the glaze:
2 cups confectioners’ sugar, sifted
3½ tablespoons freshly squeezed lemon juice
Preheat the oven to 350°. Grease, flour, and line the bottom of two 8½ X 4½ X 2½-inch loaf pans with parchment paper.
Cream the margarine and 2 cups granulated sugar in the bowl of an electric mixer fitted with the paddle attachment, for about 5 minutes, or until light and fluffy. With the mixer on medium speed, add the eggs, one at a time, and the lemon zest.
Sift together the flour, baking powder, baking soda, and salt in a bowl. In another bowl, combine ¼ cup lemon juice, the pareve milk, the vinegar, and vanilla. Add the flour and pareve milk mixtures alternately to the batter, beginning and ending with the flour. Divide the batter evenly between the pans, smooth the tops, and bake for 45 minutes to 1 hour, until a cake tester comes out clean.
Combine ½ cup granulated sugar with ½ cup lemon juice in a small saucepan and cook over low heat until the sugar dissolves.
When the cakes are done, let them cool for 10 minutes, then invert them onto a rack set over a tray, and spoon the lemon syrup over the cakes. Allow the cakes to cool completely.
For the glaze, combine the confectioners’ sugar and lemon juice in a bowl, mixing with a wire whisk until smooth. Pour over the top of the cakes and allow the glaze to drizzle down the sides.