Preheat oven to 400°F. Line a baking sheet with parchment paper or brush a cast iron skillet with melted butter.
In a medium bowl, whisk together buttermilk and mayonnaise. Add flour, mixing until fully moistened.
Turn dough out onto a lightly floured surface and turn to coat with flour until it's no longer sticky. Pat dough into a circle 3/4 inches thick. Use a 2 1/2 inch biscuit cutter dipped in flour to cut into rounds. Place on pan side by side. Brush tops with melted butter.
Bake for 20-25 minutes or until golden brown and puffed. (Increase oven to broil to brown the tops further at the end of baking.)
Serve immediately with butter and jam, stuffed with eggs, bacon or sausage for breakfast or smothered with sausage gravy.
Notes
If you don't have buttermilk on hand you can make your own. To every one cup of whole milk add 1 tablespoon of lemon juice or white distilled vinegar. Let stand for 5 minutes, then stir and proceed with the recipe.
To convert all purpose flour to self rising flour for this recipe use the same amount (3 cups) of all purpose flour adding 4 teaspoons of baking powder, 1 teaspoon of baking soda and 3/4 teaspoon of salt.
Want to skip the rolling and cutting? Butter the wells of a standard size cupcake pan and use a scoop to drop the dough dropping into the buttered cups. Bake per the recipe.