Preheat oven to 400 degrees F. Line a muffin pan with paper muffin liners (or spray the pan with cooking spray). Set aside.

Using an electric mixer, cream together the butter and sugar in a large bowl. Add the eggs and vanilla extract, and mix to combine. 

In a separate bowl, mix together the dry ingredients: all-purpose flour, whole wheat flour, salt, baking powder, and the lemon zest (which, I suppose isn't a dry ingredient, but is best added at this point). 

Alternate the addition of the dry ingredients and milk to the egg mixture, mixing until the ingredients are just combined and batter is still lumpy. (Do not overmix!) 

Gently fold the chopped strawberries into the batter. Portion batter into the prepared muffin pan, filling each muffin approximately 3/4 full. 

Bake muffins at 400 degrees F for 5 minutes. Then, leaving muffins in the oven (and oven door closed), reduce the heat to 375 degrees F. Bake the muffins for an additional 15-17 minutes, or until the centers spring back when touched and the toothpick test comes out clean. 

Remove muffins from muffin pan and allow to cool. Serve muffins warm with soft butter!