Preheat oven to 180 degrees C. Grease a loaf tin. Whisk together the matzo flour, bicarb soda, baking powder and salt in a large mixing bowl.
In a separate bowl, beat the eggs, white sugar, margarine, vanilla essence, 1 teaspoon of lemon essence, lemon juice, vegetable oil and food colouring with an electric mixer set on medium speed until smooth; pour the wet ingredients into the matzo mixture. Stir until combined into a smooth batter and pour into the prepared loaf tin.
Bake in the preheated oven until set and lightly browned, about 45 minutes. A toothpick inserted in the centre of the loaf will come out clean. Cool completely then remove from the tin.
Place 1 cup of icing sugar in a bowl. In a separate small bowl, mix the coffee whitener with water and stir in 1 tablespoon of icing sugar. Stir the coffee whitener mixture into the icing sugar by teaspoons until the mixture forms an even, workable glaze. Mix in 1/2 teaspoon of lemon essence. Spread the glaze over the cooled lemon loaf. Allow to set then serve in 2cm slices.
Look for special Kosher baking powder and Kosher icing sugar, both made with potato starch instead of cornflour, at specialty and Jewish supermarkets.