Preheat oven to 375 degrees.

Line 12 muffin tins with paper liners or grease/spray with cooking spray.

To make topping, mix all four ingredients in a bowl and pinch together to make large crumbs.

Set bowl in the freezer while making the rest of the muffins.

To make muffins, whisk together flour, baking powder and soda, cinnamon and salt. Set aside.

In a large mixing bowl, mix together butter, sugar, eggs, vanilla and Kefir.

Stir dry ingredients into wet ingredients, stirring only until combined.  

Let batter sit for five minutes.

Spoon batter into muffin tins.  

Top each muffin with the crumb topping. (If necessary, break crumbs apart with fork before using.)  

Press down a bit to make sure crumbs stick.

Bake 18-20 minutes or until golden.