Mix together flour, brown sugar, baking powder and cinnamon with a whisk, until no lumps remain.
Using a pastry blender, cut in butter until the size of small peas.
Set aside 1 cup for the crumb topping.
Add 2 tsp baking soda to 1 1/2 cups buttermilk and whisk together.
Add 2 beaten eggs to the buttermilk mixture.
Whisk with a fork. Pour into the remaining dry mixture.
Stir well with a wooden spoon until all the dry ingredients are incorporated into the wet ingredients.
Spread into a 9×13 inch parchment-lined baking pan. Top with reserved crumbs.

Bake at 350 degrees for 30 minutes or until a toothpick inserted into the center comes out clean.