Set a rack in the middle level of the oven and preheat to 400 degrees.
In a mixing bowl, combine the flour, sugar, baking powder, soda and salt and stir well to mix.
Add the butter and rub in until the butter disappears into the dry ingredients.
Stir in the caraway seeds if used and the raisins.
In a small bowl, whisk the buttermilk and egg together and mix into the dough mixture with a rubber spatula.
Turn the dough out on a floured work surface and fold it over on itself several times, shaping it into a round loaf. Transfer the loaf to one cookie sheet or jelly roll pan covered with parchment or foil and cut a cross in the top. Bake for 15 minutes then reduce heat to 350 and cook for about 15 to 20 minutes more, until well colored and a toothpick plunged into the center emerges clean.
Cool the soda bread on a rack and serve with plenty of sweet butter and bitter orange marmalade.