Orange-Banana Nut Muffins

4 tbsp. cold unsalted butter
2 cups all-purpose flour 
1 cup sugar
1 1/2 tsp baking powder
1/2 tsp baking soda 
1 tsp salt 
Juice from 1 lemon + orange juice 
    to equal 3/4 cup juice total
zest from 1 orange and 1 lemon 
1 egg
3 overripe bananas mashed 
1/2 cup chopped pecans 

Heat oven to 400 degrees.  Line muffin tin with muffin cups. 

Stir together the dry ingredients.  Cut the butter into bits, then use your fingers to rub the butter into the dry ingredients until there are no pieces bigger than a small pea.  

Whisk the juice, zest and egg together.  Pour in to the dry ingredients, mixing just enough to moisten.  Fold in the fruit and nuts, then spoon the batter into the muffin tin.  Bake for 20 minutes.  Cook on baking sheet for 15 minutes before removing.