There are quite a few. 'Bulma and Vegeta: An Unlikely Love' is a fanfic that starts from the very beginning of their relationship. It details how Bulma was initially intrigued by Vegeta's strength and how Vegeta gradually came to respect and love Bulma for her tenacity. It also has some really interesting sub - plots involving their friends and family's reactions to their relationship.
Well, 'The Bulma - Vegeta Connection' is a fanfic that's worth reading. It shows how their different personalities, Bulma's intelligence and Vegeta's pride, blend together in their relationship. There's also 'Vegeta's New World with Bulma' which delves into how Vegeta adapts to a more domestic life with Bulma and the challenges they face together.