Preheat the oven to 375°F (190°C).
In a large bowl of food processor, combine all the dry ingredients. Add buttermilk until the dough form a soft ball, but is not too sticky. Process 30 seconds in the food processor (or 3 minutes kneading by hand). The dough should be smooth and elastic. Let the dough rest for a few minutes.
Put parchment paper on a baking sheet or pan and shape the dough into a round loaf. Slash the top with a razor blade. Bake for 45 minutes or more, until the loaf’s crust is golden brown and the loaf sounds hollow when you thump the bottom.
Let cool thoroughly.
This soda bread does not keep very long, plan on eating it within a day or two. If the loaf dries out, cut and toast slices.