Puree squash in a food processor or blender for avout 2 minutes, until smooth.
4
Preheat oven to 350 F. Coat 12-cup muffin pan with cooking spray or line with baking cups.
5
In a large bowl, beat the sugar and margarine with a wooden spoon. Stir in the yougurt, blueberries, yellow squash puree, egg, lemon extract, and lemon zest.