01 -
Heat the oven to 350°F. Line a 9x5-inch metal loaf pan with parchment, leaving overhang on two sides.
02 -
In a large bowl, whisk almond flour, coconut flour, sweetener, baking powder, cinnamon, and salt until evenly combined and free of lumps.
03 -
Add eggs, sour cream, melted butter, and vanilla. Stir until the batter is thick, smooth, and evenly moistened.
04 -
In a small bowl, stir together the swirl sweetener, cinnamon, and melted butter until sandy and damp.
05 -
Spread half the batter in the pan. Sprinkle the cinnamon mixture over it, cover with the remaining batter, and drag a knife through once or twice to make a loose swirl.
06 -
Bake for 40-48 minutes, until the top is golden, the center feels set, and a toothpick comes out with moist crumbs but no wet batter. Tent with foil if the top browns too quickly.
07 -
Cool in the pan for 15 minutes, then lift out and cool on a rack for at least 45 minutes before slicing.