Preheat the oven to 350°F and spray a muffin tin with cooking spray.
Puree spinach by adding ¾ cups of it to a blender along with the vanilla, eggs, oil and applesauce. Blend until mixed together.
In a large bowl, combine all the dry ingredients – flour, sugar, baking powder, baking soda and salt.
Add the wet ingredients from the blender and mix the wet and dry ingredients until a batter forms. Pour into muffin tins so each muffin is ⅔ full.
Bake for 20 minutes at 350°F or until a toothpick inserted into the center comes out clean.