A brown butter and sour cream quick bread with a wide ribbon of cinnamon Honeycrisp apples through the middle, a cinnamon sugar crust, and a poured vanilla glaze.
2tablespoonswhole milk, only if needed to loosen the batter
Apple filling
2 ¼cupssmall diced Honeycrisp apples (from about 2 medium apples, with another 1/2 cup diced and reserved for the topping)
2tablespoonsbrowned butter, reserved from the batter step
⅔cuppacked light brown sugar
2teaspoonsground cinnamon
⅛teaspoonground cardamom
1teaspoonvanilla extract
pinchfine sea salt
1tablespoonall-purpose flour
Apple cinnamon sugar topping
½cupsmall diced Honeycrisp apples, reserved from the filling
2tablespoonsgranulated sugar
1teaspoonground cinnamon
Vanilla glaze
1 ½cupspowdered sugar
1teaspoonvanilla extract
pinchfine sea salt
2 to 3tablespoonswhole milk
Instructions
Heat the oven to 350 degrees F. Grease a standard 9x5-inch loaf pan and line it with parchment paper, leaving an overhang on the long sides.
Brown Butter
Place 1/2 cup unsalted butter in a light-colored saucepan over medium heat. Cook until it foams and the milk solids turn deep golden brown and smell nutty, about 5-7 minutes.
Pour it into a heatproof bowl right away, setting 2 tablespoons aside for the apple filling. Let the rest cool for about 10 minutes.
Apple Filling
While the butter is cooling, in a medium bowl, combine 2 1/4 cups small diced Honeycrisp apples (from about 2 medium apples, with another 1/2 cup diced and reserved for the topping), 2 tablespoons browned butter, reserved from the batter step, 2/3 cup packed light brown sugar, 2 teaspoons ground cinnamon, 1/8 teaspoon ground cardamom, 1 teaspoon vanilla extract, a pinch fine sea salt, and 1 tablespoon all-purpose flour.
Toss until every cube is evenly coated. If the apples are especially juicy, let the mixture stand 5 minutes and stir again before layering.
Batter
In a medium bowl, whisk together 1 3/4 cups all-purpose flour, 1 3/4 teaspoons baking powder, 1/4 teaspoon baking soda, and 1/2 teaspoon fine sea salt.
In a large bowl, whisk the cooled browned butter with 3/4 cup granulated sugar until well combined. Beat in 2 large eggs, room temperature one at a time,
Then stir in 2 teaspoons vanilla extract.
Add half the flour mixture and mix just until incorporated.
Add 3/4 cup full-fat sour cream. If the batter feels unusually thick, stir in up to 2 tablespoons of milk.
Fold in the remaining flour mixture just until no dry streaks remain. Do not overmix.
Spread half the batter evenly in the prepared pan.
Spoon all of the apple filling over it in an even layer.
Then carefully spread the remaining batter over the apples and smooth it to the edges.
Scatter the reserved 1/2 cup diced apples over the surface. Stir 2 tablespoons granulated sugar and 1 teaspoon ground cinnamon together and sprinkle it evenly over the loaf.
Bake at 350 degrees F for 20 minutes, then reduce the oven to 325 degrees F without opening the door. Continue baking for 40-45 minutes, until a toothpick inserted in the center comes out clean or with a few moist crumbs, or the center registers 200 to 205 degrees F. If the top browns too quickly, tent it loosely with foil for the last 15 to 20 minutes.
Cool the loaf in the pan for 15 minutes, then lift it out by the parchment and move it to a cooling rack.
Glaze
Whisk 1 1/2 cups powdered sugar, 1 teaspoon vanilla extract, a pinch fine sea salt, and enough milk to make a thick but pourable glaze.
Once the loaf is just barely warm, drizzle the glaze generously over the top and let it run down the sides. Let the glaze set before slicing.
Notes
An instant-read thermometer is the most reliable way to check doneness here. The center should register 200 to 205 degrees F, since baked apple can read as raw batter on a toothpick.
Let the loaf cool completely before slicing for the cleanest layers.