Preheat oven to 350°F (175°C) and grease or line a loaf pan.
Toss the diced apples with the brown sugar substitute, cinnamon, and lemon juice. Set aside.
Mix the cinnamon swirl ingredients together until combined.
Whisk all wet ingredients together until smooth.
In a separate bowl, mix all dry ingredients.
Add the dry mixture to the wet and stir until just combined.
Add almond milk as needed until you have a thick but pourable batter.
Pour half the batter into the loaf pan.
Add half the apples and cinnamon swirl, then lightly swirl with a knife.
Add the remaining batter, then top with the remaining apples and cinnamon swirl. Lightly swirl again.
Bake for about 45–55 minutes, or until the center is set and a toothpick comes out mostly clean.
Let cool before removing from the pan.
Mix powdered sugar substitute with a little water until thick and drizzle over the loaf.
