Preheat oven to 425 degrees. Sift together flour, sugar, baking powder, and salt. In a separate bowl, beat together milk, beaten egg, butter, and lemon zest.
Mix pears and nuts into flour mixture. Gently stir milk mixture into dry ingredients. The batter should be lumpy, not smooth. Do not over mix.
Spray muffin pans with nonstick spray. Fill muffin cups 3/4 full. Bake for 20 to 25 minutes, until tops are browned. Remove from pan immediately and serve warm.