In a large skillet over medium heat, add ground beef, breaking it into small pieces as it browns, cooking for about 5-7 minutes until no pink remains. Mix in half a chopped onion and sauté until translucent, approximately another 3 minutes. Stir in minced garlic and cumin, allowing them to become fragrant, about 1 minute.

Take one large flour tortilla and lay it flat. Spoon a generous amount of the beef and onion mixture into the center, then sprinkle with shredded cheese. Fold the tortilla sides over the filling and roll from the bottom up. Repeat with remaining tortillas.

Heat vegetable oil in a deep frying pan over medium heat until it reaches around 350°F. Carefully place 2-3 chimichangas seam-side down in the hot oil. Fry for about 3-4 minutes on each side until golden brown and crispy.

Remove the chimichangas from the oil using a slotted spoon and let them drain on paper towels. Allow to cool slightly before serving with salsa, sour cream, or guacamole.