In a large skillet over medium heat, add the ground beef. Cook until no longer pink, breaking it up with a wooden spoon as it cooks. This should take about five to seven minutes. You want the beef to be nicely browned.
Drain any excess grease from the skillet, then return the beef to the pan. Continue cooking for a couple more minutes until the beef develops a rich, brown color.
Add the garlic paste, onion powder, salt, tomato sauce, and red pepper flakes (if using). Stir well to combine all the ingredients. Let this mixture simmer for a few minutes, allowing the flavors to meld together.
In a separate large skillet over medium-low heat, add ½ tablespoon of butter and let it melt. This is essential for achieving that golden, crispy exterior.
Place one tortilla in the skillet. On one half of the tortilla, add a generous amount of Colby jack cheese, followed by a portion of the beef mixture, then top with more cheese to help everything stick together.
Fold the tortilla over to cover the filling. Spread a little butter on the top side of the tortilla to promote even browning.
Carefully flip the quesadilla over after a few minutes, cooking until all of the cheese is melted and the tortilla is golden brown. You might want to use a spatula to help with this.
Repeat the process for each quesadilla, adding more butter to the skillet as needed. You can keep the cooked quesadillas warm in the oven while you finish the rest.