1. Heat oven to 350.
2. Grease and flour the bottom only of a loaf pan.
3. Mix flour, salt, baking soda and baking powder; set aside.
4. Beat butter, sugar and vanilla in a large bowl with a mixer on medium speed until fluffy.
5. Add eggs, one at a time, beating well after each addition.
6. Beat in flour mixture alternately with yogurt, beating until smooth after each addition.
7. Remove 1 cup of the batter, stir in dry coffee
8. Pour half of the plain batter into the pan.
9. Drop coffee batter by spoonfuls onto batter in pan.
10. Add remaining plain batter.
11. Swirl batters deeply with handle of a spoon for marbled design.
12. Bake until a toothpick inserted in the center comes out clean (about an hour).
13. Cool 10 minutes.
14. Loosen sides of loaf from pan and set on a wire rack.
15. Cool completely before slicing.