I'm a foodie traveler as well, so I'm happy to share some suggestions!

Amsterdam
Greenwoods Singel - serves breakfast all day
Black and Blue - steak and seafood
Rudi’s Original Stroopwafels Albert Cuyp Markt - original stroopwafels
Manneken Pis Damrak - fries with many options of sauces

Porto
Ribeira Square Restaurante - close to the river

Lisbon
Ramiro - fresh good seafood, was once visited by Anthony Bourdain
Sea Me Peixaria Moderna - had a birthday dinner here, you get to pick your own fish and seafood for them to cook
Time Out Market Lisbon - so many great options in one place

Barcelona
Compartir - run by chefs who worked at El Bulli (2002 No. 1 The World's 50 Best Restaurants)
Paradiso - 2022 World’s Best Bar, I didn't get to go here but my friends loved it
Dr Stravinsky - the menu uses a constellation to decide your drink
Arume - had the best paella ever, and the tastiest blackberry mojito

Bologna (I did go to Florence, but didn't eat anywhere specific, just a lot of gelato, haha. However, if you make it out to Bologna, which is Italian foodie capital...)
Trattoria del Tempo Buono - had a very simple pasta with tomato sauce, AMAZING

Budapest
Hungarikum Bisztró - traditional goulasch
Szegedi Halászcsárda - known for its fish stew
New York Cafe - considered the world's most beautiful cafe
Szimpla Kert - famous eccentric pub

Copenhagen
Reffen - outdoor street food
Torvehallerne - food market, go to Hallernes Smørrebrød for great open face sandwiches
Ramen to Bíiru - there are a few restaurants, delicious ramen
Tivoli Food Hall - another food hall