3 to 3 ½ cups of all-purpose flour
1 teaspoon baking soda
2 teaspoons salt
1 ½ cups buttermilk (shake the bottle before pouring)
1 cup raisins
And here are the original instructions from the Stay at Home Chef:

Preheat oven to 425 degrees Fahrenheit.
In large bowl whisk together 2 ½ cups flour, salt, and baking soda. Add in your buttermilk and raisins (if using) and stir until it just comes together.
Turn out onto lightly floured surface and knead until it forms a smooth ball. Gradually add more flour as necessary to achieve a dough that is firm and not sticky.
Dust the outside with flour and place on an un-greased baking sheet. Use a sharp knife to slash a one inch deep cross on top of the loaf.
Bake in oven for 35 minutes or until golden brown.