Horse Soup

Today I was telling my Spanish teacher about the soup I made last night.
She asked what the ingredients were and I told her, in Spanish of course:

Broccoli, red pepper, salt, pepper, cumin, mustard, and...horses.

I meant to say cebollas (onions) but I said caballos (horses) instead.

She looked at me, confused, and I immediately realized my mistake. We had a good laugh and I assured her I don't cook with horse meat.