In small bowl, stir together flour, poppy seeds, salt and baking soda. In large bowl, cream sugar and butter. Beat in eggs one at a time. Add yogurt and vanilla extract; mix well. Stir in flour mixture until dry ingredients are moistened. Spoon batter into greased muffin tins.
Bake at 400° for 15-20 minutes or until a toothpick inserted in center of muffin comes out clean. Cool on wire rack for 5 minutes before removing from pan.