Pair this quesadilla filling with queso fresco, Monterey Jack, and guacamole.
Heat a saute pan over medium-low heat; add olive oil. When hot, add onion; saute until translucent, about 5 minutes.
Add mushrooms and epazote; cook until mushrooms are tender and most of the liquid has evaporated, about 5 minutes. Add lemon juice; season with salt and pepper.
Dried oregano can be substituted for epazote.