Preheat oven to 160ºC Spray 8- 1 cm Pyrex loaf dish with Pam. Cream butter with sugar on high speed of mixer for 5 minutes. Add 1 egg and then a little flour, beating 2 minutes. Add 2nd egg and half of remaining flour and beat 2 minutes. Add sour cream, rest of flour and extract, beating 2 minutes. Spread batter evenly in dish. Bake for 65 minutes or until tester comes out clean. Remove from dish. Slice 1 cm thick. Be sure to slice before freezing loaf. Thaw to use within 6 months.