Preheat oven to 375°F. Line a standard 12-cup muffin tin with paper liners. Spritz the liners with nonstick spray; set aside.
In a medium bowl, whisk together flour, baking powder, baking soda and salt. Set aside.
In a large bowl, use an electric mixer on low speed to combine the oil and ¾ cup of sugar. Increase the speed to medium-high and continue mixing for 2 more minutes. Add the eggs, one at a time, mixing to combine after each addition. Mix in the vanilla extract, the optional orange zest (if using), and the sour cream until smooth. With the mixer on low speed, gradually add the dry ingredients. Mix just until the batter is thick and smooth; do not over-mix.
In a small bowl, toss together the cranberries and the remaining 2 tablespoons of sugar so that all of the cranberries are coated. Using a spatula or wooden spoon, gently fold the cranberries into the batter.
Divide the batter evenly between the prepared muffin cups. Sprinkle tops with optional coarse sugar, if desired.
Bake for 18-22 minutes, or until a toothpick inserted in the center of a muffin comes out clean.
Remove the muffins from the pan and transfer to a wire rack to cool completely.