Preparation Steps

• Heat oven to 345°F. Line two 8×4-inch loaf pans with parchment, leaving overhang for easy lifting, and lightly grease the parchment.
• In a small bowl, stir together the cinnamon and 1/2 cup sugar for the swirl; set aside.
• Whisk the dry ingredients: flour, baking soda, salt, and nutmeg in a medium bowl until evenly combined.
• In a large bowl with a hand mixer or stand mixer, cream the softened butter with 1 3/4 cups granulated sugar and 1/4 cup brown sugar on medium-high until very light and fluffy, 3 to 4 minutes, scraping the bowl once or twice.
• Beat in the eggs one at a time on medium speed until fully incorporated and glossy, 30 seconds each.
• On low speed, add the dry ingredients in three additions, alternating with the buttermilk in two additions, beginning and ending with the dry. Mix just until the flour streaks disappear; do not overmix.
• Let the batter rest 10 minutes to hydrate the flour for a softer crumb.
• Divide about two-thirds of the batter between the pans and level the tops. Evenly sprinkle about two-thirds of the cinnamon-sugar over the batter. Spoon the remaining batter on top, then finish with the remaining cinnamon-sugar. Use a butter knife to make two gentle figure-eight passes through each loaf to marble the layers.
• Bake 50 to 60 minutes, rotating pans halfway. Loaves are done when a toothpick inserted near the center comes out with a few moist crumbs or the internal temperature reads 202–205°F. Tip: If the tops are browning too quickly, tent loosely with foil at the 40-minute mark.
• Cool in pans on a rack for 15 minutes, then lift out using the parchment and cool completely before slicing for the cleanest swirls.