1/2 cup sweet creamy butter, softened

2/3 cup sugar

2 large eggs, separated

1 1/3 cups flour

1 teaspoon baking powder

1/2 teaspoon baking soda

2 tablespoons poppy seeds

2 lemons, zest of, grated

1/4 teaspoon salt

1/2 cup buttermilk or plain yogurt

2 tablespoons lemon juice

1 teaspoon vanilla 

Preheat oven to 350°F Coat muffin tin with nonstick cooking spray.

In a large bowl, cream the butter and sugar until fluffy.  Add the egg yolks, one at a time.  Beat well after each.  In a separate bowl, stir together the dry ingredients, poppy seeds, and lemon zest.

With the mixer on low speed, add the dry ingredients to the creamed mixture, alternating two times with the buttermilk, then lemon juice, and then vanilla.  Beat just until smooth.  In another bowl, beat the egg whites until soft peaks form.  Gently fold them into the muffin batter until blended.  Spoon the batter into the prepared pan, 3/4-full.