In large saute pan, heat 1 tablespoon of olive oil. When the oil begins to smoke, add the onions and jalapeno. Cook for 3 minutes until onions are translucent. Add tomatoes, and cook for 2 more minutes. Add the mustard greens. Cook for 5 minutes until greens are wilted and tender. Add the lemon juice and season with salt and pepper. Serve.
Recipe courtesy of Aaron Sanchez