Tap Air Portugal has round-trip flights from Newark/New York (JFK/EWR) to Porto or Lisbon (OPO/LIS) for $309-$329, NONSTOP. Flights October to March. Extended weekends available.
Carry on bag with a maximum weight of 17.6 lbs is allowed for free on TAP. You can avoid seat selection fees by accepting the randomly assigned seat at the gate. Upgrading to a higher fare class that includes a carry-on bag for $65 may be cheaper than booking the “Discount” fare with the added $95 carry-on bag fee.