If you are a buth gulla like I am and like small portions with minimal conversation, we recommend Kaema Laasthi. They also have a huge plus point which other delivery services don't have, which I'll get to in a moment.
The ordering is straight forward. We inboxed them our details with a location. They follow up with a confirmation text and the time your lunch will be dropped off. For the first time round, it would be easier if you also sent them a location map.
The menus are posted daily on their FB page. For today's menu we ordered an egg rice packet which includes a mildly spicy omelette which was a tad too salty for my tastebuds, cabbage white curry, red dhal curry, white raddish tempered and a gottukola salad and all of this accompanied by a sambol. The egg rice packet is Rs. 165, while the fish is Rs. 175 and the chicken is Rs. 185. Which I think is a pretty decent price to pay for a good buth packet.
Kaema Laasthi's plus point is that they do not incur a delivery charge when almost everyone else does and we end up paying an exorbitant price. All you pay for is the amount of your lunch packet and their delivery personnel are polite and very pleasant.
If you prefer less talk while ordering, small quantity of rice and don't enjoy your mouth on fire, Kaema Laesthi is your go to place (rather ordering in place). Right now their delivery is limited to Colombo 4 and Colombo 3.
Place your order before 10:30 AM daily.