Onion soup with grilled cheese and toast, in my house in Amsterdam, 2022.
Whenever I want to make some comfort food for my father, I often come back to good French onion soup. Naturally, a variation of onion soup would have been a dish for the poor, also in North-Western Europe, where they have been cultivated for at least hundreds of years. The French bistro version of onion soup is a bit more decadent, with its wine, butter, and cheese. For some references, see Wikipedia and NYT Cooking.
Caramelize shredded onions in a heavy pan in butter for an hour or so. Take care to not burn them. Deglaze with white wine and add good broth. Season with salt and pepper. Ladle into bowls and cover with slices of nice bread. Grate cheese on top, and put under the broiler for a few minutes.
Serve with more ground black pepper and maybe some fresh herbs.