1. In a large cast-iron pan, heat the olive oil. Add the garlic, onion and jalapeño and cook over moderately high heat, stirring occasionally, until softened, about 3 minutes.
2. Stir in the tomatoes, collards, bay leaves and thyme sprigs. Cover and cook over moderately low heat, stirring occasionally, until the collards are tender, about 20 minutes.
3. Discard the jalapeño, bay leaves and thyme sprigs. Season the collards with salt and pepper and serve.
Make Ahead: The dish can be refrigerated overnight and reheated gently on the stovetop.