I think 30 minutes is rushing it unless you tend to eat really quickly. When we are at a restaurant, we like to enjoy the food rather than rush through it.
As mentioned, if you ask fo rthe chek up front, you can leave any time that you wish.
Boma has the standard breakfast fare, but then has a lot of other interesting things to try.
For us, it takes much longer than 30 minutes. YMMV.
As mentioned, if you want to be out quickly, why not do Mara instead?