Blueberry Muffins with Crumbled Topping

I've been making these blueberry muffins for as long as I can remember. I love the crumble topping on them. Of course I always have to double them because they get eaten pretty quickly. Makes for a great go-to breakfast.

Blueberry Muffins

1 c. flour
1 tsp. baking powder
1/4 tsp. salt
1/2 c. sugar
2 tsp. lemon juice
1/2 c. butter
2 eggs
3/4 c. blueberries (I mostly use frozen)

Mix dry ingredients together and set aside.
Cream butter, sugar, eggs and lemon juice. Slowly add the flour mixture until smooth. Fold in blueberries.

Place scoops of the batter into the muffin tins. Then top with the following topping:

1 T sugar
2 T chopped walnuts
1/4 t. cinnamon

Bake for 25 minutes in a preheated 350 degree oven.