Thanks for the pearl sugar link, BakerAunt. It gave me an, "Oh my" moment. My pearl sugar completely coated the centers of the muffins. Around the edges, it was sprinkled properly. I put the sugar directly on the batter, so the sugar adhered to the muffins.
I agree with the writer of the link that cardamom goes great with citrus. When I make Oatmeal Coffee Cake, I use cardamom even though it's not in the recipe and the orange flavor comes from orange oil (KABC).