In a large skillet, heat over medium heat and brown the ground beef until fully cooked, about 5-7 minutes. Add the chopped onion and minced garlic, sautéing for another 5 minutes until tender. Stir in ground cumin, chili powder, smoked paprika, salt, and black pepper, and cook for 1 more minute. Stir in the tomato sauce and let it simmer for 5 minutes until thickened. Mix in the shredded cheddar and Monterey Jack cheese until melted.

Warm the flour tortillas in the microwave for 10-15 seconds until soft and pliable. This prevents cracking when rolled. Keep them covered with a kitchen towel to maintain warmth.

Place about ⅓ cup of the cheesy beef mixture in the center of each tortilla. Fold in the sides and roll tightly from the bottom up to secure the filling. Ensure a tight seal and repeat until all chimichangas are assembled.

Heat vegetable oil in a deep skillet to 350°F (175°C). Carefully place the chimichangas seam-side down into the hot oil, frying in batches. Fry for about 3-4 minutes per side until golden brown and crispy. Drain on paper towels to absorb excess oil.

Serve the hot chimichangas alongside a platter of your favorite toppings like shredded lettuce, diced tomatoes, sour cream, guacamole, or salsa. Pair them with Mexican rice or refried beans for a complete meal.