Heat the olive oil in a large skillet over medium-high heat.

Add the diced onion and cook for 3–4 minutes, until softened.

Add the ground beef and cook until browned, breaking it apart as it cooks.

Drain excess grease if needed.

Stir the taco seasoning into the browned beef.

Add the drained Rotel diced tomatoes and green chilies.

Pour in the water or beef broth.

Simmer for 5–7 minutes, stirring occasionally, until slightly thickened.

Season with salt and black pepper to taste.

Melt the butter in a saucepan over medium heat.

Whisk in the flour and cook for about 1 minute.

Slowly pour in the milk while whisking constantly.

Cook for 3–5 minutes, until the sauce has thickened.

Reduce the heat to low.

Gradually stir in the shredded cheddar and Monterey Jack cheese.

Add the taco seasoning and garlic powder.

Stir until the cheese has melted and the sauce is smooth and creamy.

Warm the tortillas in a dry skillet or microwave.

Fill each tortilla with the seasoned beef mixture.

Spoon a generous amount of the cheesy Rotel sauce over the beef.

Top with shredded lettuce, diced tomatoes, red onion and fresh cilantro.

Serve immediately with lime wedges.

Add sour cream if desired.