From what I can find they are simple carbs. Is this correct?
Per 100g, onions have 9.34g total carbs - 3.4g complex carbs, 4.24g simple carbs, and 1.7g fiber.
See here: https://fdc.nal.usda.gov/fdc-app.html#/food-details/170000/nutrients
The answer depends on what definition of “complex carb” you use.
Onions have glucose, fructose, and sucrose - all simple carbs.
They also have fructans, which are fructose chains. By one definition they are complex carbs, but most complex carbs are glucose chains.
For metabolic purposes I would consider them as simple carbs, but I think the distinction between simple and complex carbs isn’t meaningful metabolically as a chain of glucose is metabolized pretty much like a the same amount of glucose.
Here’s a paper with more information on onions.
Kinda shocked no one has said that onions are a vegetable!
While they contain carbs, it’s probably one of the least important nutritional aspects of onions.
Being in the allium genus, they have anti-inflammatory properties. They are full of phytochemicals, vitamins, minerals, and fibre. They are very healthy.
If you’re getting pedantic about the macros in onions you may be suffering from an unhealthy relationship with food and some disordered eating.