Preheat the oven to 300 degrees F (150 degrees C). Grease a tube pan.

Sift flour and salt together into a bowl. Mix milk and lemon extract together in a separate bowl.

Combine sugar, butter, and shortening in a large bowl; beat with an electric mixer until creamy. Add eggs one at a time, beating until well combined. Mix in the flour mixture alternately with the milk mixture, beginning and ending with flour. Spread batter in the prepared pan.

Bake in the preheated oven until a toothpick inserted into the center comes out clean, about 2 hours. Do not open the oven door while the cake is baking. Cool briefly in the pan before inverting onto a wire rack to cool completely.