Heat a large skillet over medium heat and brown 1 pound of ground beef, stirring until fully cooked, about 5 minutes. Add 1 diced onion and 2 minced garlic cloves, cooking until softened, another 5 minutes. Sprinkle in 1 teaspoon each of ground cumin, chili powder, and smoked paprika, along with salt and pepper to taste. Pour in 1 cup of tomato sauce, stirring well, and let simmer for an additional 5 minutes until the mixture thickens.

Remove the skillet from heat and mix in 1 cup each of shredded cheddar and Monterey Jack cheese. Stir until the cheeses are melted and well combined with the beef mixture. Set aside to cool slightly.

Warm four large flour tortillas in the microwave for 30 seconds to make them pliable. Take a tortilla, spoon 1/3 cup of the beef filling into the center, fold in the sides, and roll from the bottom up to secure the filling. Repeat this process with all tortillas.

In a deep skillet, heat vegetable oil to 350°F (175°C). Carefully place the chimichangas seam-side down into the hot oil, frying in batches, for about 3-4 minutes on each side until golden brown and crispy, turning only once.

Plate your crispy Cheesy Beef Chimichangas and serve them warm with shredded lettuce, diced tomatoes, sour cream, and guacamole. Enjoy!