In a skillet, cook the ground beef with chopped onion and garlic over medium heat until browned.

Add chili powder and cumin, stirring to combine. Cook for an additional 5 minutes.

Warm the corn tortillas in a separate skillet or microwave.

Assemble tacos by placing the beef mixture on tortillas and topping with lettuce, tomatoes, and cheese.

In a bowl, mash the avocados with lime juice.

Stir in onion, garlic, cilantro, and salt until well combined.

In a bowl, combine diced tomatoes, onion, jalapeño, lime juice, cilantro, and salt.

Mix well and let sit for 10 minutes to allow flavors to meld.