Question Best Beach Towns Near Lisbon or Porto?

I'm planning a trip to Portugal and looking for the best beach towns near Lisbon or Porto. I'm especially interested in places that are not too crowded but still have a good vibe, with nice beaches and maybe some local culture or good food. I've heard about Cascais and Nazaré, but I'm wondering if there are any hidden gems I should consider. Any recommendations for a month-long stay?