Talk to Mikael about Carlotta

Walkthrough
If the Dragonborn speaks with Carlotta Valentia, the fruit and vegetable vendor in the Whiterun marketplace, she will mention that the bard, Mikael will not leave her alone. The Dragonborn can then offer to speak with Mikael about his behaviour. Mikael will be in the inn, The Bannered Mare.

If the Dragonborn's speech skill is sufficiently high, a simple talking-to will suffice. Otherwise, intimidation might be necessary. The Dragonborn can also choose to brawl with Mikael. Sprich mit Mikael über Carlotta