No — dangerous
No — cats are even more sensitive to onion toxicity than dogs. All alliums (onion, garlic, leek, chive) destroy feline red blood cells, in any form: raw, cooked or powdered.
N-propyl disulfide and related compounds oxidise haemoglobin and rupture red blood cells, causing haemolytic anaemia — and the feline version of haemoglobin is structurally more vulnerable to this damage than the canine one. A 4 kg cat can be poisoned by as little as 5 g of onion per kg (a couple of tablespoons of cooked onion). The most common real-world source isn’t raw onion — it’s onion powder in baby food, broths, gravies, soups and seasoned meats fed as “treats”.
None, in any form. Read labels on anything savoury you share: stock cubes, broths and deli meats almost always contain onion or garlic powder. If exposure happens, call your vet — anaemia signs can take days.
For safe savoury flavour, plain meat juices from unseasoned cooked chicken work; never stock or gravy.
This article is general information, not veterinary advice. If your pet has eaten something potentially harmful or shows symptoms, contact your vet or an emergency clinic immediately. Full disclaimer.