A versatile and delicious lemon blueberry muffin recipe with a buttery, crunchy cinnamon crumble topping. Adapted from Family Circle Cookbook and [Fifteen Spatulas|http://www.fifteenspatulas.com/blueberry-meyer-lemon-muffins-with-streusel-crumb-topping/].
!To make the topping:
In a small mixing bowl, stir together the sugar, flour, cinnamon, and salt. Add the cubed butter and, using a pastry blender, cut in the butter until the mixture resembles coarse crumbs. Place topping mixture into the refrigerator while you prepare the batter.
!To make the muffins:
Preheat oven to 400. Line a 12-count muffin tin with paper liners.
In a larger mixing bowl, stir together the flour, sugar, baking powder, salt, and lemon zest. In a small bowl, whisk together the oil, milk, and egg until well combined. Pour the wet ingredients into the dry ingredients and stir together until just combined (no need to get all the lumps out when making muffins; over mixing the dough produces dense muffins). Gently fold in the blueberries (you will find that there are just as many blueberries as there is batter and you may fear there's not enough batter and you've done something wrong. Don't worry. This is how you want it to be so that your muffins are packed with blueberries as pictured).
Divide the batter between the twelve muffin cups (I used my medium cookie scoop with heaping portions to do this). Sprinkle each muffin generously with the crumble topping. You will likely have a little topping leftover.
Bake the muffins 20-22 minutes (if using frozen berries, bake 24-26 minutes instead) until cooked through and golden. Allow to cool at least 15 minutes before removing from the pan.