Whisk together the spelt flour, baking powder, baking soda, and sea salt in a large bowl.
In a medium bowl, mash the banana and add the applesauce, honey, oil, chia seeds and lemon zest. Whisk until well blended. Add the lemon juice and stir briefly to mix.
Add the wet mixture to the dry ingredients, stir gently just until flour is mixed in.
Fold in the blueberries.
Quickly spoon the batter into muffin tins and place in the oven. I use silicone muffin tins, so no need for greasing the tray. If using a metal muffin tin lightly grease or use baking paper, before spooning mixture in.
Bake for about 22 mins, until center springs back when touched.
Let cool in the pan for 5-10 minutes, then move to a cooling rack.
Makes 10-12 regular sized muffins or 8 extra large muffins.