In a large skillet over medium-high heat, cook ground beef and onion until meat is browned and onion is soft, approximately 7-9 minutes.
Drain excess grease from the skillet and stir in minced garlic, chili powder, cumin, salt, and pepper. Cook for an additional 2 minutes.
Warm tortillas slightly to make them pliable. Spread 2 tablespoons of refried beans in the center of each tortilla.
Layer the beef mixture and shredded cheese over the beans.
Fold the left and right sides of the tortilla toward the center, then roll tightly from the bottom to create a sealed cylinder.
In a heavy-bottomed pan or deep fryer, heat 1 inch of oil to 375 degrees Fahrenheit.
Fry the chimichangas in batches, seam-side down first, for 2 to 3 minutes per side until golden brown.
Remove with tongs and drain on paper towels to remove excess oil before serving.