Creating these Leftover Cranberry Sauce Coffee Cake Muffins is a breeze if you follow these clear steps:

1. Preheat Your Oven: Begin by preheating your oven to 350°F (175°C). Line a muffin tin with paper liners or grease it lightly.
2. Mix Dry Ingredients: In a large bowl, whisk together the flour, granulated sugar, brown sugar, baking powder, baking soda, salt, and cinnamon until well combined.
3. Combine Wet Ingredients: In another bowl, mix the melted butter, eggs, vanilla extract, leftover cranberry sauce, and sour cream until smooth.
4. Combine Mixtures: Gradually add the wet ingredients to the dry ingredients, stirring until just combined. Be careful not to overmix; a few lumps are okay.
5. Add Nuts (Optional): If you’re adding nuts, fold them into the batter now for added texture.
6. Fill Muffin Cups: Spoon the batter into the prepared muffin tin, filling each cup about 2/3 full.
7. Bake: Place the muffin tin in the preheated oven and bake for 25-30 minutes or until a toothpick inserted into the center comes out clean.
8. Cool: Once baked, remove the muffins from the oven and let them cool in the pan for about 5-10 minutes. Then transfer them to a wire rack to cool completely.

These simple steps will guide you in creating these incredible muffins effortlessly.