Position oven rack in the center of the oven; preheat oven to 400°.
Prepare muffin tins: spray indentations and the rims with nonstick cooking spray.
In a bowl, whisk flour, sugar, cornmeal, baking soda, and salt until well combined; set aside.
In a big bowl, whisk the egg and sour cream until smooth.
Whisk in the tequila, orange juice, oil, lime juice, and zest until well blended.
Stir in the flour mixture with a wooden spoon until incorporated.
Fill muffin tins ¾ full; if desired, sprinkle 1/8 teaspoon coarse salt over muffin top before baking (coarse salt gives the topping a little bite; if you don’t like margaritas in salt-rimmed glasses, you probably should omit this).
Bake for 20 minutes or until the tops are lightly browned and cracked.
Set pan on wire rack to cool for 10 minutes; gently rock each muffin back and forth to release and remove from tin.
Cool muffins for 5 minutes on the rack before serving.
*Margarita Pumpkin Seed Muffins: add ¾ cup toasted, shelled pumpkin seeds (pepitas) with the flour.
*Sugar-Topped Margarita Muffins: omit the coarse salt; sprinkle the muffins with ½ teaspoon coarse or colored sugar before baking.