Preheat the oven to 350 degrees F. Spray and lightly flour (do not use muffin liners as these stick) 7-9 of the muffin cavities and set aside.
Remove 1 tablespoon from the flour and return it to the flour bag. In a bowl, toss together the remaining flour with the cornstarch and baking powder until well mixed. (When you measure the flour make sure to spoon and level the flour not to pack it into the measuring cup)
Stir in the well drained fruit cocktail (drain WELL or these muffins will be soggy) until well coated in the flour mixture and set aside.
In another bowl (important to use 2 bowls so the ingredients don't get over-mixed resulting in dense muffins), lightly beat the egg with a fork for 20 seconds. Stir in the Greek yogurt, vanilla extract, and melted coconut oil until well combined.
Stir in the sugar and mix until smooth.
Add the dry ingredients to the wet and mix until JUST combined. Over-mixing will yield less optimal results.
Fill up the prepared muffin tin a little over 3/4ths the way full.
Bake for 25-30 minutes or until a fork when inserted in the center comes out clean.