Warm the olive oil in a large skillet over medium heat.
Add the onion and saute until soft, about 4 minutes.
Add the garlic and jalapeño and saute until fragrant, about 1 minute.
Add the ground beef and seasonings and cook browned, about 6 to 8 minutes.
Add the collard greens and tomatoes and saute until wilted, about 4 minutes.
Stir everything gently as it cooks, careful not to mush the tomatoes.
Add the lemon juice, season with salt and pepper to taste and serve.