Take a 20 km drive, from Cascais, in a beautiful road through the Sintra hills until you arrive to the famous Praia Grande (means “Big Beach”)
The spectacular location, alone, would do the trick, on the beach with some majestic Cliffs (check here), but there is also great food, specially the seafood!
Great also for some drinks outside by the sunset.
In winter, dinner inside with fireplace is also good idea.
Just 12 Kms away, in case you have some time, don’t leave Portugal without a visit to Palacio da Pena