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

Add onion and garlic to the skillet and sauté until softened.

Stir in chili powder, cumin, salt, and black pepper. Mix well and remove from heat.

Add shredded cheddar cheese to the beef mixture and stir until melted.

Place a generous amount of the beef and cheese filling in the center of each tortilla.

Fold the sides of the tortilla over the filling, then roll it up tightly from the bottom.

Secure with toothpicks if necessary.

Heat vegetable oil in a deep fryer to 350°F (175°C).

Carefully place chimichangas in the hot oil, a few at a time, and fry until golden brown, about 3-4 minutes per side.

Remove from oil and drain on paper towels.

Serve hot with sour cream, salsa, and guacamole on the side.