Step #1 In a bowl, with a mixer on high speed, beat butter & sugar until smooth.
Step #2 Add egg & beat well.
Step #3 Beat in orange juice.
Step #4 In another bowl, orange peel, mix flour, salt, baking powder, & baking soda.
Step #5 Stir half the flour mixture into the butter mixture, followed by the rest of the flour mixture, then the buttermilk, until just incorporated.
Step #6 Spoon batter equally into 24 buttered miniature muffin c or 12 regular muffin c (1/3 c).
Step #7 Bake in a 350° regular or convection oven until tops are lightly browned & a wooden skewer inserted into the center of one muffin comes out with moist crumbs attached, 20 to 25 mins.
Step #8 Invert pan to remove cakes.
Step #9 Serve warm, or let cool to about room temp.