Preheat the oven to 350*F. Spray a muffin tin with cooking spray. In a large bowl sift together the flour, baking powder, salt and sugar. This makes for a light muffin!
In a separate and smaller mixing bowl, mix the egg, yogurt, milk and melted butter together. Make a well in the center of the dry ingredients and pour the wet mixture into the center. Mix gently, only until the ingredients are combined. Add 2/3 of the lemon curd and quickly "blend" it through the batter.
Fill the muffin cups 3/4 full. Bake for 30 minutes until golden brown. Transfer to a wire rack to slightly cool. I scoop out a little center in each muffin and place a good teaspoon of the remaining lemon curd inside and on top of each muffin! Serve slightly warm! If you love lemons, then you are gonna make these many, many times!