While the Economy menu is specifically included for LowFare+ and Flex tickets, it's only available via pre-order for LowFare.
From https://www.norwegian.com/us/travel-info/on-board/food-and-drinks/international-long-haul-flights/
LowFare
If you're flying on a LowFare ticket, our Economy menu is available to
pre-order. Keep in mind that pre-ordering your meal must be done at
least 72 hours prior to departure. Don't feel like having a full meal
on board? The snack bar is open between servings, so you won't go
hungry.
LowFare+ and Flex
If you've booked a LowFare+ or Flex ticket, the Economy menu is
included for your flight.
https://www.norwegian.com/us/travel-info/on-board/food-and-drinks/international-long-haul-flights/
There's a price list for pre-ordered meals as well as individual snacks and drinks on the Optional service charges page here.
https://www.norwegian.com/us/booking/booking-information/optional-charges/
International long haul
Pre-ordered meals - LowFare tickets
- 45 USD per person, each way
Snacks and drinks on board
Light meals, snacks and drinks are available for purchase on board
most flights. Onboard purchases may be charged in a different currency
than stated below. Prices may change without notice.
- Non-alcoholic drinks: 4 - 5 USD
- Alcoholic drinks: 7 - 15 USD
- Snacks: 4 - 8 USD
- Fresh food: 10 - 11 USD
The Economy menu is described here at Norwegian's site here:
https://www.norwegian.com/us/travel-info/on-board/food-and-drinks/international-long-haul-flights/
First service
- A cold pasta/salad starter
- For the main course you’ll get either a meat or fish dish with vegetables and potatoes or rice
- The meal is rounded off with a dessert
- Coffee/tea is served after the meal
Second service
- A snack bag which includes a sandwich, a sweet or savoury treat and a juice box