Preheat oven to 325 degrees F (165 degrees C). Grease and flour a 10 inch bundt pan. Sift together the flour, baking soda and salt. Set aside.
In a large bowl, cream together the margarine and sugar until light and fluffy. Beat in the eggs one at a time, then stir in the lemon extract. Alternately beat in the flour mixture and the yogurt, mixing just until incorporated.
Pour batter into a 10 inch Bundt pan. Bake in the preheated oven for 60 minutes, or until a toothpick inserted into the center of the cake comes out clean. Allow to cool 10 minutes in the pan, then turn out onto a wire rack and cool completely.