The protagonist has a crush on a girl who is now a widow. Where does the yaoi come into this story? Not knowing makes it harder to figure this one out.

Tenshi no Tamagoryouri - this is the only title I can think that is at all similar. The protagonist had a male lover, but then married. After his wife dies, the lover is back in the picture.

Here's a couple good ones set in a restaurant. Maybe they can keep you busy until you find what you want. 😃
Dolce
Suki to Iu no ni Naze Kashira
Umaimon Kuwasero!

Up!