How to Make It
In a large pot, heat the olive oil. Add the onion, garlic and jalapeño and cook over moderate heat until softened, about 6 minutes.
Add the greens, season with salt and pepper and toss to wilt. Stir in the tomatoes, water and vinegar, cover and cook over low heat, stirring occasionally, until the greens are tender and the tomatoes are soft, 10 to 15 minutes. Transfer to a bowl and serve.