In a large bowl mix together the flour, sugar, baking powder, baking soda, salt, and cinnamon.
In another bowl using an electric mixer beat the eggs, and then mix in the melted butter, buttermilk, and lemon zest until well combined.
Mix the egg mixture with the flour mixture until combined. (You want this to be just moistened – don’t over mix the batter will be lumpy.) Gently fold in the berries.
To make the topping mix all the ingredients together in a small bowl until crumbly. (Using a fork works well for this to help distribute the butter.)
Lightly spray a jumbo muffin tin with cooking spray, and spoon the batter into the muffin cups. Sprinkle the topping evenly over the top of each muffin.
Bake for 20 to 30 minutes until muffins are golden brown and a toothpick inserted comes out clean. (These muffins are pretty big so I used a wooden skewer to check for doneness.)
Let cool 10 minutes, remove to a cooling rack to cool, or serve warm with butter.