In a skillet over medium heat, cook the ground beef until browned. Drain excess fat.

Add chili powder, cumin, garlic powder, and onion powder to the meat. Stir well and cook for an additional 5 minutes.

Remove from heat and mix in shredded cheese until melted.

Heat vegetable oil in a frying pan over medium-high heat.

Place a corn tortilla in the hot oil and cook for about 30 seconds until it starts to bubble.

Using tongs, fold the tortilla in half and continue frying until golden brown and crispy, about 2-3 minutes.

Remove from oil and drain on paper towels. Repeat with remaining tortillas.

Fill each crispy taco shell with the beef filling, then top with shredded lettuce, diced tomato, and a dollop of sour cream.