Zapple Muffins

Zapple Sauce: 4 cups peeled, seeded and diced zucchini or summer squash 1/3 cup fresh lemon juice 1/2 cup packed light brown sugar 2 teaspoons ground cinnamon 1/4 teaspoon ground nutmeg For Muffin Batter: 1/2 cup butter, softened, plus more...