Questions & Answers about Linsen mit Brokkoli sind für mich ein gutes Mittagessen.
Because the grammatical subject is Linsen mit Brokkoli, and the head noun there is Linsen, which is plural.
So German makes the verb agree with Linsen, not with Mittagessen.
- Linsen ... sind ... = Lentils ... are ...
- Das Mittagessen ist gut. = The lunch is good.
Even though ein gutes Mittagessen is singular, it is the complement after sein, not the subject.
In German, Linse means lentil in the singular, and Linsen is the normal plural form.
When talking about lentils as food, German often uses the plural:
- Ich esse gern Linsen. = I like eating lentils.
So Linsen mit Brokkoli is a very natural way to mean lentils with broccoli.
Because the sentence is speaking about lentils in a general sense, not a specific set of lentils.
German often uses no article with plural nouns when talking about things in general:
- Hunde sind freundlich. = Dogs are friendly.
- Linsen sind gesund. = Lentils are healthy.
If you meant specific lentils, you could use an article:
- Die Linsen mit Brokkoli sind lecker. = The lentils with broccoli are tasty.