burning onions

A person is said to be "burning onions" when they are having a hard time accomplishing a specific goal.

Unlike "spinning your wheels" this phrase does not contain any insinuations of harming the environment with toxic smoke. In fact, onions are better to eat than wheels, so it's really the healthier of the two phrases.

Sal: My apartment is already full of plants and I'm burning onions trying to find room for my new Aloe Vera plant!
Luces: Oh no, I hope you can make room for it!