Boil 3 C water in a saucepan. When it begins to boil add your lemon and simmer for 20 minutes.
Pre heat the oven to 350F. Line a muffin tray with parchment cups and set aside
In a mixing bowl combine all the dry ingredients, set aside
When the lemon has finished cooking remove it from the hot water and slice into wedges, removing seeds and ends. Puree the lemon in a food processor or blender
In a second mixing bowl combine all the wet ingredients including 1/2 of the lemon puree (note: You cooked a whole lemon but you're only using half in the recipe)
Pour the wet ingredients into the mixture with the dry ingredients until combined
Fold in the blueberries
Divide the batter into the muffin cups
*If using the crumble topping make it now and divide among the muffins
Bake for about 22 minutes until cooked through