Preheat oven to 425°. Whisk together the first 5 ingredients. Work the peanut butter into the flour mixture with your hands, two knives or a pastry cutter until it resembles coarse meal. Mix in the raisins.
Add the buttermilk and mix with a wooden spoon or your hands for about 2 minutes. Don’t overmix or it will become too stiff. Let the dough sit for a few minutes for the buttermilk to soak into the oats. Grease a baking sheet and place the dough on the baking sheet. Use your hands or a spoon to shape the dough into a round loaf that is about 3-4 inches tall in the center. Use a serrated knife to make a cross on top of the bread.
Bake for 35-40 minutes, until the loaf is golden brown and sounds hollow when tapped. Remove from the oven and let cool on the baking sheet for 5 minutes, then transfer to a cooling rack or prop the loaf on it’s side so the top and bottom of the loaf are both exposed to the air (so it doesn’t get moist).