An entire ground lemon goes into the mix, giving these muffins a deep lemon flavour. Plain yoghurt combines with the lemon to create a muffin that is both tangy and sweet. This is a modified version of another recipe on recipzaar.com.
Preheat the oven to 350°F Grease 12 large size muffin cups with butter or cooking spray or line with paper muffin wrappers.
Wash and dry the lemon. Cut into quarters and remove the seeds. Process the quartered lemon (all of it) in a food processor, or blender, fitted with a metal blade for 1-minute or more until it is completely ground up. Scrape the lemon into a small bowl, and set aside for later use.
Using a mixer fitted with a paddle attachment, cream the butter in a large bowl on medium high speed for 1 minute. Scrape down the sides of the bowl. Add the Splenda and beat on medium high until light and fluffy. Add the egg whites all at once and beat on medium speed for 1 minute. Add the vanilla and beat for about 30-seconds. Mix together the dry ingredients. Beat one third of it into the creamed mixture just until incorporated. Add half the yoghurt and do the same. Repeat, ending with dry ingredients. Gently stir in the lemon.
Spoon batter into prepared muffin tins. Bake for 30-minutes until they spring back when gently touched, or a toothpick inserted in the center comes out clean. Let cool in the pans for 5 minutes, then remove to a wire rack.
These are at their very best served warm, but if wrapped tightly in plastic wrap once cooled, they will still taste great for up to 3 days. They can be frozen for up to 3 weeks.