Preheat: Heat the oven to 350°F (175°C) and grease and line a loaf pan with parchment paper.
Whisk: In a large bowl, whisk together 2 eggs, ½ cup Greek yogurt, ¼ cup honey, 1 teaspoon vanilla, lemon zest, and lemon juice until smooth.
Add: Stir in 1 ½ cups almond flour, 1 ½ cups oat flour, 1 teaspoon baking powder, ½ teaspoon baking soda, and a pinch of salt until just combined. The batter will be thick.
Divide: Split the batter evenly between two bowls.
Crush: Add ½ cup frozen blueberries to one bowl and gently crush some with the back of a spoon to release juices and tint the batter.
Swirl: Alternate scoops of lemon batter and blueberry batter into the prepared loaf pan, then gently swirl with a knife.
Bake: Bake for 40–50 minutes, until golden on top and a toothpick inserted in the center comes out clean.
Cool: Let the loaf cool in the pan for 10 minutes, then transfer to a rack to cool completely before slicing.
Notes
If the top starts browning too quickly, just loosely tent it with foil while you finish the baking time.
Frozen blueberries are actually ideal here because they bleed less into the batter when you swirl.
This loaf slices best once it’s fully cool. I know it’s tempting, but give it a minute.
If you want more lemon punch, add extra zest. I almost always do.