My dog ate a lot more that usual today. Her tummy is quite bloated and hard. She is laying down and is not active. Her meal contained chicken and unions.
Onions can cause damage to red blood cells if sufficient quantities are eaten as it is one of the main foods to avoid: https://www.vetbabble.com/dogs/food-and-diet-dogs/10-foods-bad-for-dogs/
I would recommend reading this article about what to do:
As it suggests, you should call the ASPCA poison control to find out if the dose your dog ate is a threat.