Learn Spanish (Latin America): Es una costumbre típica; solemos cenar en el patio. - It is a typical custom; we usually have dinner on the patio.

Like other stem-changing verbs in the present tense (such as poder or dormir), the nosotros form does not change its stem. The letter 'o' stays exactly as it is, giving us solemos.

Can I just say normalmente cenamos to mean 'we usually have dinner'?

Yes, normalmente cenamos or usualmente cenamos are both completely correct and mean the same thing. However, using soler followed by an infinitive (like solemos cenar) is a very natural and common way for native speakers to express habits, so it is a highly useful structure to master.

Why use the verb cenar instead of translating 'have dinner' literally as tener la cena?

In Spanish, the daily meals have their own dedicated verbs. While la cena is the noun for 'dinner', you use the single verb cenar to say 'to eat dinner' or 'to have dinner'. Translating 'have dinner' literally with the verb tener sounds unnatural in Spanish.

Is the word costumbre always feminine?