Spaghetti carbonara is always a winner. A lot of people make it with garlic but traditionally it’s just guanciale (or pancetta or bacon depending on what’s available for you), eggs, cheese, and noodles. It’s the Italian bacon egg and cheese. There are plenty of good recipes but whichever one you choose, the key to getting the emulsification right is to mix the cheese and eggs together cold and then add them to the pasta heat off while stirring quickly. Add the leftover water from boiling the pasta in small amounts until you get the consistency you want. The sauce should be creamy, not thin or chunky.

There are some communities that feel garlic or regular onions are too strong, and substitute the white of leeks. It does affect the resulting taste, but if your wife tolerates them, it’s an option.

My own suggestions for recipes would include some classic Slavic dishes where onions aren’t essential. These do exist, 😁 particularly ones that mix sweet, sour and savoury flavours. e.g., Crepes/nalasnyky filled with farmers’ cheese and butter or cream, traditionally served with sour cherry or strawberry preserves on top, are a favourite. For a savoury version, try these nalasnyky with dill in the cheese filling.

Is this part of a low fodmap diet or just a food preference thing? Either way you can get a lot of decent recipes just searching low fodmap x.

also pasta with roasted or sauteed cherry tomatoes is my go to, top with basil/parm/whatevs

Unfortunately, 40% of every dish I make is yellow onion and garlic so I don’t think I can help.

Maybe wife is vampire

So possibly try some Romanian cabbage rolls https://www.jocooks.com/recipes/sarmale/ Substitute onions with green onions since you said green onions are fine however you can also remove them if you wish as they just go into a mix of the beef