Heat olive oil in a large skillet over medium heat.
Add the diced onion and cook until softened, about 3-4 minutes.
Add the garlic and cook for another minute.
Add the ground beef to the skillet and cook until browned, breaking it up with a spoon as it cooks. Drain any excess fat.
Season:
Stir in the taco seasoning, making sure the beef is evenly coated. If using store-bought seasoning, follow the packet instructions for water addition (typically 1/4 cup).
Add Cabbage:
Add the shredded cabbage to the skillet. Stir well to combine and cook until the cabbage is tender, about 5-7 minutes.
Optional Add-Ins:
If using diced tomatoes, stir them in and cook for another 2-3 minutes.
Sprinkle shredded cheddar cheese on top if desired, and let it melt.
Serve:
Taste and adjust seasoning with salt and pepper as needed.
Serve with optional toppings like sour cream, chopped cilantro, sliced jalapeños, and lime wedges.