Preheat the oven to 350°F (175°C). Generously butter two 9×5-inch loaf pans.

Place the 5 cups sifted all-purpose flour in a large mixing bowl.

Add the 3/4 cup granulated sugar, 2 teaspoons baking powder, 1 1/2 teaspoons salt, and 1 teaspoon baking soda to the flour; stir to combine.

Cut the 1/2 cup unsalted butter into small cubes and work it into the flour mixture with your fingers or a pastry cutter until the mixture looks grainy and resembles coarse crumbs.

Place the 2 1/2 cups raisins in a bowl and pour hot (not boiling) water over them; let them soak 15–20 minutes. Drain the raisins well and blot lightly if needed to remove excess surface moisture.

Stir the drained raisins and 3 tablespoons caraway seeds into the flour-butter mixture until evenly distributed.

In a separate bowl, whisk together the 2 1/2 cups buttermilk and 1 large egg until combined.

Pour the buttermilk-and-egg mixture into the flour mixture and stir gently until just combined; the batter should be a thick cake-batter consistency.

Divide the batter evenly between the two prepared loaf pans, smoothing the tops. Sprinkle turbinado sugar over each loaf.

Bake on the center oven rack for 60–70 minutes, or until a toothpick inserted into the center of each loaf comes out clean or with only a few moist crumbs.

Remove the pans from the oven and let the loaves cool in the pans for 3–5 minutes. Then transfer the loaves to a wire rack to cool completely before slicing.